AIM 2/20/25
capability will be listed in the PBN box. The separate Equipment Requirements box will list ground −based
equipment and/or airport specific requirements. On procedures with both PBN elements and ground −based
equipment requirements, the PBN requirements box will be listed first. (See FIG 5−4−1.)
c. Other RNP Applications Outside the U.S. The FAA and ICAO member states have led initiatives in
implementing the RNP concept to oceanic operations. For example, RNP−10 routes have been established in the
northern Pacific (NOPAC) which has increased capacity and efficiency by reducing the distance between tracks
to 50 NM. (See paragraph 4−7−1.)
d. Aircraft and Airborne Equipment Eligibility for RNP Operations. Aircraft eligible for RNP operations
will have an appropriate entry including special conditions and limitations in its AFM, avionics manual, or a
supplement. Operators of aircraft not having specific RNP eligibility statements in the AFM or avionics
documents may be issued operational approval including special conditions and limitations for specific RNP
eligibilities.
NOTE−
Some airborne systems use Estimated Position Uncertainty (EPU) as a measure of the current estimated navigational
performance. EPU may also be referred to as Actual Navigation Performance (ANP) or Estimated Position Error (EPE).
TBL 1−2−1
U.S. Standard RNP Levels
RNP Level Typical Application Primary Route
Width (NM) −
Centerline to
Boundary
0.1 to 1.0 RNP AR Approach Segments 0.1 to 1.0
0.3 to 1.0 RNP Approach Segments 0.3 to 1.0
1 Terminal and En Route 1.0
2 En Route 2.0
4 Oceanic/remote areas where performance−based horizontal
separation is applied.
4.0
10 Oceanic/remote areas where performance−based horizontal
separation is applied.
10.0
1−2−3. Use of Suitable Area Navigation (RNAV) Systems on Conventional Procedures and
Routes
a. Discussion. This paragraph sets forth policy, while providing operational and airworthiness guidance
regarding the suitability and use of RNA V systems when operating on, or transitioning to, conventional,
non−RNA V routes and procedures within the U.S. National Airspace System (NAS):
1. Use of a suitable RNA V system as a Substitute Means of Navigation when a V ery−High Frequency (VHF)
Omni−directional Range (VOR), Distance Measuring Equipment (DME), Tactical Air Navigation (TACAN),
VOR/TACAN (VORTAC), VOR/DME, Non−directional Beacon (NDB), or compass locator facility including
locator outer marker and locator middle marker is out −of−service (that is, the navigation aid (NA V AID)
information is not available); an aircraft is not equipped with an Automatic Direction Finder (ADF) or DME;
or the installed ADF or DME on an aircraft is not operational. For example, if equipped with a suitable RNA V
system, a pilot may hold over an out−of−service NDB.
2. Use of a suitable RNA V system as an Alternate Means of Navigation when a VOR, DME, VORTAC,
VOR/DME, TACAN, NDB, or compass locator facility including locator outer marker and locator middle
marker is operational and the respective aircraft is equipped with operational navigation equipment that is
compatible with conventional navaids. For example, if equipped with a suitable RNA V system, a pilot may fly
a procedure or route based on operational VOR using that RNA V system without monitoring the VOR.
1−2−8 Performance−Based Navigation (PBN) and Area Navigation (RNA V)
AIM2/20/258/7/25 AIM
NOTE−
1. Additional information and associated requirements are available in Advisory Circular 90-108 titled “Use of Suitable
RNAV Systems on Conventional Routes and Procedures.”
2. Good planning and knowledge of your RNAV system are critical for safe and successful operations.
3. Pilots planning to use their RNAV system as a substitute means of navigation guidance in lieu of an out −of−service
NAVAID may need to advise ATC of this intent and capability.
4. The navigation database should be current for the duration of the flight. If the AIRAC cycle will change during flight,
operators and pilots should establish procedures to ensure the accuracy of navigation data, including suitability of
navigation facilities used to define the routes and procedures for flight. To facilitate validating database currency, the F AA
has developed procedures for publishing the amendment date that instrument approach procedures were last revised. The
amendment date follows the amendment number, e.g., Amdt 4 14Jan10. Currency of graphic departure procedures and
STARs may be ascertained by the numerical designation in the procedure title. If an amended chart is published for the
procedure, or the procedure amendment date shown on the chart is on or after the expiration date of the database, the
operator must not use the database to conduct the operation.
b. Types of RNA V Systems that Qualify as a Suitable RNA V System. When installed in accordance with
appropriate airworthiness installation requirements and operated in accordance with applicable operational
guidance (for example, aircraft flight manual and Advisory Circular material), the following systems qualify as
a suitable RNA V system:
1. An RNA V system with TSO−C129/ −C145/−C146 equipment, installed in accordance with AC 20−138,
Airworthiness Approval of Global Positioning System (GPS) Navigation Equipment for Use as a VFR and IFR
Supplemental Navigation System, and authorized for in strument flight rules (IFR) en route and terminal
operations (including those systems previously qualified for “GPS in lieu of ADF or DME” operations), or
2. An RNA V system with DME/DME/IRU inputs that is compliant with the equipment provisions of AC
90−100A, U.S. Terminal and En Route Area Navigation (RNA V) Operations, for RNA V routes. A table of
compliant equipment is available at the following website:
https://www.faa.gov/about/office_org/headquarters_ offices/avs/offices/afx/a fs/afs400/afs410/media/
AC90−100compliance.pdf
NOTE−
Approved RNAV systems using DME/DME/IRU, without GPS/WAAS position input, may only be used as a substitute means
of navigation when specifically authorized by a Notice to Airmen (NOTAM) or other F AA guidance for a specific procedure.
The NOTAM or other F AA guidance authorizing the use of DME/DME/IRU systems will also identify any required DME
facilities based on an F AA assessment of the DME navigation infrastructure.
c. Uses of Suitable RNA V Systems. Subject to the operating requirements, operators may use a suitable
RNA V system in the following ways.
1. Determine aircraft position relative to, or distance from a VOR (see NOTE 6 below), TACAN, NDB,
compass locator, DME fix; or a named fix defined by a VOR radial, TACAN course, NDB bearing, or compass
locator bearing intersecting a VOR or localizer course.
2. Navigate to or from a VOR, TACAN, NDB, or compass locator.
3. Hold over a VOR, TACAN, NDB, compass locator, or DME fix.
4. Fly an arc based upon DME.
NOTE−
1. The allowances described in this section apply even when a facility is identified as required on a procedure (for example,
“Note ADF required”).
2. These operations do not include lateral navigation on localizer −based courses (including localizer back− course
guidance) without reference to raw localizer data.
3. Unless otherwise specified, a suitable RNAV system cannot be used for navigation on procedures that are identified as
not authorized (“NA”) without exception by a NOTAM. For example, an operator may not use a RNAV system to navigate
Performance−Based Navigation (PBN) and Area Navigation (RNA V) 1−2−9
AIM 2/20/25
on a procedure affected by an expired or unsatisfactory flight inspection, or a procedure that is based upon a recently
decommissioned NAVAID.
4. Pilots may not substitute for the NAVAID (for example, a VOR or NDB) providing lateral guidance for the final approach
segment. This restriction does not refer to instrument approach procedures with “or GPS” in the title when using GPS or
WAAS. These allowances do not apply to procedures that are identified as not authorized (NA) without exception by a
NOTAM, as other conditions may still exist and result in a procedure not being available. For example, these allowances
do not apply to a procedure associated with an expired or unsatisfactory flight inspection, or is based upon a recently
decommissioned NAVAID.
5. Use of a suitable RNAV system as a means to navigate on the final approach segment of an instrument approach procedure
based on a VOR, TACAN or NDB signal, is allowable. The underlying NAVAID must be operational and the NAVAID
monitored for final segment course alignment.
6. For the purpose of paragraph c, “VOR” includes VOR, VOR/DME, and VORTAC facilities and “compass locator”
includes locator outer marker and locator middle marker.
d. Alternate Airport Considerations. For the purposes of flight planning, any required alternate airport must
have an available instrument approach procedure that does not require the use of GPS. This restriction includes
conducting a conventional approach at the alternate airport using a substitute means of navigation that is based
upon the use of GPS. For example, these restrictions would apply when planning to use GPS equipment as a
substitute means of navigation for an out−of−service VOR that supports an ILS missed approach procedure at
an alternate airport. In this case, some other approach not reliant upon the use of GPS must be available. This
restriction does not apply to RNA V systems using TSO−C145/−C146 WAAS equipment. For further WAAS
guidance, see paragraph 1−1−18.
1. For flight planning purposes, TSO-C129() and TSO-C196() equipped users (GPS users) whose
navigation systems have fault detection and exclusion (FDE) capability, who perform a preflight RAIM
prediction at the airport where the RNA V (GPS) approach will be flown, and have proper knowledge and any
required training and/or approval to conduct a GPS-based IAP, may file based on a GPS-based IAP at either the
destination or the alternate airport, but not at both locations. At the alternate airport, pilots may plan for
applicable alternate airport weather minimums using:
(a) Lateral navigation (LNA V) or circling minimum descent altitude (MDA);
(b) LNA V/vertical navigation (LNA V/VNA V) DA, if equipped with and using approved barometric
vertical navigation (baro-VNA V) equipment;
(c) RNP 0.3 DA on an RNA V (RNP) IAP, if they are specifically authorized users using approved
baro-VNA V equipment and the pilot has verified required navigation performance (RNP) availability through
an approved prediction program.
2. If the above conditions cannot be met, any required alternate airport must have an approved instrument
approach procedure other than GPS that is anticipated to be operational and available at the estimated time of
arrival, and which the aircraft is equipped to fly.
3. This restriction does not apply to TSO-C145() and TSO-C146() equipped users (WAAS users). For
further WAAS guidance, see paragraph 1−1−18.
1−2−4. Recognizing, Mitigating, and Adapting to GPS Jamming and/or Spoofing
a. The low−strength data transmission signals from GPS satellites are vulnerable to various anomalies that
can significantly reduce the reliability of the navigation signal. The GPS signal is vulnerable and has many uses
in aviation (e.g., communication, navigation, surveillance, safety systems and automation); therefore, pilots
must place additional emphasis on closely monitoring aircraft equipment performance for any anomalies and
promptly inform Air Traffic Control (ATC) of any apparent GPS degradation. Pilots should also be prepared to
operate without GPS navigation systems.
b. GPS signals are vulnerable to intentional and unintentional interference from a wide variety of sources,
including radars, microwave links, ionosphere effects, solar activity, multi−path error, satellite communications,
1−2−10 Performance−Based Navigation (PBN) and Area Navigation (RNA V)
AIM2/20/258/7/25 AIM
GPS repeaters, and even some systems onboard the aircraft. In general, these types of unintentional interference
are localized and intermittent. Of greater and growing concern is the intentional and unauthorized interference
of GPS signals by persons using “jammers” or “spoofers” to disrupt air navigation by interfering with the
reception of valid satellite signals.
NOTE−
The U.S. government regularly conducts GPS tests, training activities, and exercises that interfere with GPS signals. These
events are geographically limited, coordinated, scheduled, and advertised via GPS and/or WAAS NOTAMS. Operators of
GPS aircraft should always check for GPS and/or WAAS NOTAMS for their route of flight.
c. Manufacturers, operators, and air traffic controllers should be aware of the general impacts of GPS jamming
and/or spoofing, which include, but are not limited to:
1. Inability to use GPS for navigation.
2. Inability to use hybrid GPS inertial systems for navigation.
3. Loss of, or degraded, performance−based navigation (PBN) capability (e.g., inability to fly required
navigation performance (RNP) procedures).
4. Unreliable triggering of Terrain Awareness and Warning Systems (TAWS).
5. Inaccurate aircraft position on navigation display (e.g., moving map and electronic flight bag).
6. Loss of, or erroneous, Automatic Dependent Surveillance-Broadcast (ADS−B) outputs.
7. Unexpected effects when navigating with conventional NA V AIDS (e.g., if the aircraft is spoofed from
the intended flight path, autotuning will not select the nearby NA V AID).
8. Unanticipated position-dependent flight management system effects (e.g., erroneous insufficient fuel
indication).
9. Failure or degradation of Air Traffic Management (A TM) infrastructure and its associated systems reliant
on GPS, resulting in potential airspace infringements and/or route deviations.
10. Failure of, or erroneous aircraft clocks (resulting in inability to log on to Controller-Pilot Data Link
Communications CPDLC).
11. Erroneous wind and ground speed indications.
d. When flying IFR, pilots should have additional navigation equipment for their intended route to crosscheck
their position. Routine checks of position against VOR or DME information, for example, could help detect a
compromised GPS signal. Pilots transitioning to VOR navigation in response to GPS anomalies should refer to
the Chart Supplement U.S. to identify airports with available conventional approaches associated with the VOR
Minimum Operational Network (MON) program. (Reference 1−1−3f.)
e. Prior to departure, the FAA recommends operators to:
1. Be aware of potential risk locations.
2. Check for any relevant Notices to Airmen (NOTAMs).
3. Plan fuel contingencies.
4. Plan to use conventional NA V AIDs and appropriate arrival/approach procedures at the destination.
5. Follow the detailed guidance from the respective Original Equipment Manufacturer (OEM).
f. During flight, the FAA recommends operators do the following:
1. Be vigilant for any indication that the aircraft’s GPS is disrupted by reviewing the manufacturer’s
guidance for that specific aircraft type and avionics equipage. Verify the aircraft position by means of
conventional NA V AIDs, when available. Indications of jamming and/or spoofing may include:
(a) Changes in actual navigation performance.
Performance−Based Navigation (PBN) and Area Navigation (RNA V) 1−2−11
AIM 2/20/25
(b) Aircraft clock changes (e.g., incorrect time).
(c) Incorrect Flight Management System (FMS) position.
(d) Large shift in displayed GPS position.
(e) Primary Flight Display (PFD)/Navigation Display (ND) warnings about position error.
(f) Other aircraft reporting clock issues, position errors, or requesting vectors.
2. Assess operational risks and limitations linked to the loss of GPS capability, including any on −board
systems requiring inputs from a GPS signal.
3. Ensure NA V AIDs critical to the operation for the intended route/approach are available.
4. Remain prepared to revert to conventional instrument flight procedures.
5. Promptly notify ATC if they experience GPS anomalies. Pilots should not inform ATC of GPS jamming
and/or spoofing when flying through known NOTAMed testing areas unless they require ATC assistance. (See
paragraph 1−1−13)
g. Post flight, the FAA recommends operators to:
1. Document any GPS jamming and/or spoofing in the maintenance log to ensure all faults are cleared.
2. File a detailed report at the reporting site: Report a GPS Anomaly Federal Aviation Administration,
www.faa.gov/air_traffic/nas/gps_reports.
1−2−12 Performance−Based Navigation (PBN) and Area Navigation (RNA V)
AIM2/20/258/7/25 AIM
Chapter 2. Aeronautical Lighting and Other Airport
Visual Aids
Section 1. Airport Lighting Aids
2−1−1. Approach Light Systems (ALS)
a. ALS provide the basic means to transition from instrument flight to visual flight for landing. Operational
requirements dictate the sophistication and configuration of the approach light system for a particular runway.
b. ALS are a configuration of signal lights starting at the landing threshold and extending into the approach
area a distance of 2400 −3000 feet for precision instrument runways and 1400 −1500 feet for nonprecision
instrument runways. Some systems include sequenced flashing lights which appear to the pilot as a ball of light
traveling towards the runway at high speed (twice a second). (See FIG 2−1−1.)
2−1−2. Visual Glideslope Indicators
a. Visual Approach Slope Indicator (V ASI)
1. V ASI installations may consist of either 2, 4, 6, 12, or 16 light units arranged in bars referred to as near,
middle, and far bars. Most V ASI installations consist of 2 bars, near and far, and may consist of 2, 4, or 12 light
units. Some V ASIs consist of three bars, near, middle, and far, which provide an additional visual glide path to
accommodate high cockpit aircraft. This installation may consist of either 6 or 16 light units. V ASI installations
consisting of 2, 4, or 6 light units are located on one side of the runway, usually the left. Where the installation
consists of 12 or 16 light units, the units are located on both sides of the runway.
2. Two−bar V ASI installations provide one visual glide path which is normally set at 3 degrees. Three−bar
V ASI installations provide two visual glide paths. The lower glide path is provided by the near and middle bars
and is normally set at 3 degrees while the upper glide path, provided by the middle and far bars, is normally 1/4
degree higher. This higher glide path is intended for use only by high cockpit aircraft to provide a sufficient
threshold crossing height. Although normal glide path angles are three degrees, angles at some locations may
be as high as 4.5 degrees to give proper obstacle clearance. Pilots of high performance aircraft are cautioned that
use of V ASI angles in excess of 3.5 degrees may cause an increase in runway length required for landing and
rollout.
3. The basic principle of the V ASI is that of color differentiation between red and white. Each light unit
projects a beam of light having a white segment in the upper part of the beam and red segment in the lower part
of the beam. The light units are arranged so that the pilot using the V ASIs during an approach will see the
combination of lights shown below.
4. The V ASI is a system of lights so arranged to provide visual descent guidance information during the
approach to a runway. These lights are visible from 3−5 miles during the day and up to 20 miles or more at night.
The visual glide path of the V ASI provides safe obstruction clearance within plus or minus 10 degrees of the
extended runway centerline and to 4 NM from the runway threshold. Descent, using the V ASI, should not be
initiated until the aircraft is visually aligned with the runway. Lateral course guidance is provided by the runway
or runway lights. In certain circumstances, the safe obstruction clearance area may be reduced by narrowing the
beam width or shortening the usable distance due to local limitations, or the V ASI may be offset from the
extended runway centerline. This will be noted in the Chart Supplement and/or applicable Notices to Airmen
(NOTAMs).
Airport Lighting Aids 2−1−1
AIM 2/20/25
FIG 2−1−1
Precision & Nonprecision Configurations
NOTE−
Civil ALSF−2 may be operated as SSALR during favorable weather conditions.
2−1−2 Airport Lighting Aids
2/20/25 AIM
5. For 2−bar V ASI (4 light units) see FIG 2−1−2.
FIG 2−1−2
2−Bar VASI
Far Bar
= Red
Near Bar = White
Below Glide Path On Glide Path Above Glide Path
6. For 3−bar V ASI (6 light units) see FIG 2−1−3.
FIG 2−1−3
3−Bar VASI
Far Bar
Middle Bar
Near Bar
Below Both
Glide Paths
On Lower
Glide Path
On Upper
Glide Path
Above Both
Glide Paths
7. For other V ASI configurations see FIG 2−1−4.
FIG 2−1−4
V ASI Variations
2 Bar 2 Bar 3 Bar
2 Light Units 12 Light Units 16 Light Units
On Glide Path On Glide Path on Lower Glide Path
Airport Lighting Aids 2−1−3
AIM 2/20/25
b. Precision Approach Path Indicator (PAPI). The precision approach path indicator (PAPI) uses light units
similar to the V ASI but are installed in a single row of either two or four light units. These lights are visible from
about 5 miles during the day and up to 20 miles at night. The visual glide path of the PAPI typically provides
safe obstruction clearance within plus or minus 10 degrees of the extended runway centerline and to 3.4 NM from
the runway threshold. Descent, using the PAPI, should not be initiated until the aircraft is visually aligned with
the runway. The row of light units is normally installed on the left side of the runway and the glide path indications
are as depicted. Lateral course guidance is provided by the runway or runway lights. In certain circumstances,
the safe obstruction clearance area may be reduced by narrowing the beam width or shortening the usable
distance due to local limitations, or the PAPI may be offset from the extended runway centerline. This will be
noted in the Chart Supplement and/or applicable NOTAMs. (See FIG 2−1−5.)
FIG 2−1−5
Precision Approach Path Indicator (PAPI)
High Slightly High On Glide Path Slightly Low Low
(More Than (3.2 Degrees) (3 Degrees) (2.8 Degrees) (Less Than
3,5 Degrees) 2.5 Degrees)
White
Red
c. Tri−color Systems. Tri−color visual approach slope indicators normally consist of a single light unit
projecting a three−color visual approach path into the final approach area of the runway upon which the indicator
is installed. The below glide path indication is red, the above glide path indication is amber, and the on glide path
indication is green. These types of indicators have a useful range of approximately one−half to one mile during
the day and up to five miles at night depending upon the visibility conditions. (See FIG 2−1−6.)
FIG 2−1−6
Tri−Color Visual Approach Slope Indicator
Amber
Above Glide PathOn Glide Path
Below Glide Path
Amber
Green
Red
NOTE−
1. Since the tri−color VASI consists of a single light source which could possibly be confused with other light sources, pilots
should exercise care to properly locate and identify the light signal.
2. When the aircraft descends from green to red, the pilot may see a dark amber color during the transition from green to
red.
Airport Lighting Aids2−1−4
2/20/25 AIM
FIG 2−1−7
Pulsating Visual Approach Slope Indicator
NOTE−
Since the PVASI consists of a single light source which could possibly be confused with other light sources, pilots should
exercise care to properly locate and identify the light signal.
FIG 2−1−8
Alignment of Elements
Above Glide Path On Glide Path Below Glide Path
d. Pulsating Systems. Pulsating visual approach slope indicators normally consist of a single light unit
projecting a two−color visual approach path into the final approach area of the runway upon which the indicator
is installed. The on glide path indication may be a steady white light or alternating RED and WHITE light. The
slightly below glide path indication is a steady red light. If the aircraft descends further below the glide path, the
red light starts to pulsate. The above glide path indication is a pulsating white light. The pulsating rate increases
as the aircraft gets further above or below the desired glide slope. The useful range of the system is about four
miles during the day and up to ten miles at night. (See FIG 2−1−7.)
e. Alignment of Elements Systems. Alignment of elements systems are installed on some small general
aviation airports and are a low−cost system consisting of painted plywood panels, normally black and white or
fluorescent orange. Some of these systems are lighted for night use. The useful range of these systems is
approximately three−quarter miles. To use the system the pilot positions the aircraft so the elements are in
alignment. The glide path indications are shown in FIG 2−1−8.
Airport Lighting Aids 2−1−5
AIM 2/20/25
2−1−3. Runway End Identifier Lights (REIL)
REILs are installed at many airfields to provide rapid and positive identification of the approach end of a
particular runway. The system consists of a pair of synchronized flashing lights located laterally on each side of
the runway threshold. REILs may be either omnidirectional or unidirectional facing the approach area. They are
effective for:
a. Identification of a runway surrounded by a preponderance of other lighting.
b. Identification of a runway which lacks contrast with surrounding terrain.
c. Identification of a runway during reduced visibility.
2−1−4. Runway Edge Light Systems
a. Runway edge lights are used to outline the edges of runways during periods of darkness or restricted
visibility conditions. These light systems are classified according to the intensity or brightness they are capable
of producing: they are the High Intensity Runway Lights (HIRL), Medium Intensity Runway Lights (MIRL),
and the Low Intensity Runway Lights (LIRL). The HIRL and MIRL systems have variable intensity controls,
whereas the LIRLs normally have one intensity setting.
b. The runway edge lights are white, except on instrument runways yellow replaces white on the last 2,000
feet or half the runway length, whichever is less, to form a caution zone for landings.
c. The lights marking the ends of the runway emit red light toward the runway to indicate the end of runway
to a departing aircraft and emit green outward from the runway end to indicate the threshold to landing aircraft.
2−1−5. In −runway Lighting
a. Runway Centerline Lighting System (RCLS). Runway centerline lights are installed on some precision
approach runways to facilitate landing under adverse visibility conditions. They are located along the runway
centerline and are spaced at 50−foot intervals. When viewed from the landing threshold, the runway centerline
lights are white until the last 3,000 feet of the runway. The white lights begin to alternate with red for the next
2,000 feet, and for the last 1,000 feet of the runway, all centerline lights are red.
b. Touchdown Zone Lights (TDZL). Touchdown zone lights are installed on some precision approach
runways to indicate the touchdown zone when landing under adverse visibility conditions. They consist of two
rows of transverse light bars disposed symmetrically about the runway centerline. The system consists of
steady−burning white lights which start 100 feet beyond the landing threshold and extend to 3,000 feet beyond
the landing threshold or to the midpoint of the runway, whichever is less.
c. Taxiway Centerline Lead−Off Lights. Taxiway centerline lead−off lights provide visual guidance to
persons exiting the runway. They are color−coded to warn pilots and vehicle drivers that they are within the
runway environment or instrument landing system (ILS) critical area, whichever is more restrictive. Alternate
green and yellow lights are installed, beginning with green, from the runway centerline to one centerline light
position beyond the runway holding position or ILS critical area holding position.
d. Taxiway Centerline Lead −On Lights. Taxiway centerline lead −on lights provide visual guidance to
persons entering the runway. These “lead−on” lights are also color−coded with the same color pattern as lead−off
lights to warn pilots and vehicle drivers that they are within the runway environment or instrument landing
system (ILS) critical area, whichever is more conservative. The fixtures used for lead−on lights are bidirectional,
i.e., one side emits light for the lead−on function while the other side emits light for the lead−off function. Any
fixture that emits yellow light for the lead−off function must also emit yellow light for the lead−on function.
(See FIG 2−1−12.)
e. Land and Hold Short Lights. Land and hold short lights are used to indicate the hold short point on certain
runways which are approved for Land and Hold Short Operations (LAHSO). Land and hold short lights consist
of a row of pulsing white lights installed across the runway at the hold short point. Where installed, the lights
will be on anytime LAHSO is in effect. These lights will be off when LAHSO is not in effect.
2−1−6 Airport Lighting Aids
2/20/25 AIM
REFERENCE−
AIM, Para 4−3−1 1, Pilot Responsibilities When Conducting Land and Hold Short Operations (LAHSO).
2−1−6. Runway Status Light (RWSL) System
a. Introduction. RWSL is a fully automated system that provides runway status information to pilots and
surface vehicle operators to clearly indicate when it is unsafe to enter, cross, takeoff from, or land on a runway.
The RWSL system processes information from surveillance systems and activates Runway Entrance Lights
(REL) and Takeoff Hold Lights (THL), in accordance with the position and velocity of the detected surface traffic
and approach traffic. REL and THL are in−pavement light fixtures that are directly visible to pilots and surface
vehicle operators. RWSL is an independent safety enhancement that does not substitute for or convey an ATC
clearance. Clearance to enter, cross, takeoff from, land on, or operate on a runway must still be received from
ATC. Although ATC has limited control over the system, personnel do not directly use and may not be able to
view light fixture activations and deactivations during the conduct of daily ATC operations.
b. Runway Entrance Lights (REL): The REL system is composed of flush mounted, in-pavement,
unidirectional light fixtures that are parallel to and focused along the taxiway centerline and directed toward the
pilot at the hold line. An array of REL lights include the first light at the hold line followed by a series of evenly
spaced lights to the runway edge; one additional light at the runway centerline is in line with the last two lights
before the runway edge (see FIG 2−1−9 and FIG 2−1−10). When activated, the red lights indicate that there is
high speed traffic on the runway or there is an aircraft on final approach within the activation area.
1. REL Operating Characteristics − Departing Aircraft: When a departing aircraft reaches a site adaptable
speed of approximately 30 knots, all taxiway intersections with REL arrays along the runway ahead of the aircraft
will illuminate (see FIG 2−1−9). As the aircraft approaches an REL equipped taxiway intersection, the lights at
that intersection extinguish approximately 3 to 4 seconds before the aircraft reaches it. This allows controllers
to apply “anticipated separation” to permit ATC to move traffic more expeditiously without compromising
safety. After the aircraft is declared “airborne” by the system, all REL lights associated with this runway will
extinguish.
2. REL Operating Characteristics − Arriving Aircraft: When an aircraft on final approach is approximately
1 mile from the runway threshold, all sets of taxiway REL light arrays that intersect the runway illuminate. The
distance is adjustable and can be configured for specific operations at particular airports. Lights extinguish at
each equipped taxiway intersection appr oximately 3 to 4 seconds before the aircraft reaches it to apply
anticipated separation until the aircraft has slowed to approximately 80 knots (site adjustable parameter). Below
80 knots, all arrays that are not within 30 seconds of the aircraft’s forward path are extinguished. Once the arriving
aircraft slows to approximately 34 knots (site adjustable parameter), it is declared to be in a taxi state, and all
lights extinguish.
3. What a pilot would observe: A pilot at or approaching the hold line to a runway will observe RELs
illuminate and extinguish in reaction to an aircraft or vehicle operating on the runway, or an arriving aircraft
operating less than 1 mile from the runway threshold.
4. When a pilot observes the red lights of the REL, that pilot will stop at the hold line or remain stopped.
The pilot will then contact ATC for resolution if the clearance is in conflict with the lights. Should pilots note
illuminated lights under circumstances when remaining clear of the runway is impractical for safety reasons (for
example, aircraft is already on the runway), the crew should proceed according to their best judgment while
understanding the illuminated lights indicate the runway is unsafe to enter or cross. Contact ATC at the earliest
possible opportunity.
Airport Lighting Aids 2−1−7
AIM 2/20/25
FIG 2−1−9
Runway Status Light System
c. Takeoff Hold Lights (THL) : The THL system is composed of flush mounted, in-pavement, unidirectional
light fixtures in a double longitudinal row aligned either side of the runway centerline lighting. Fixtures are
focused toward the arrival end of the runway at the “line up and wait” point. THLs extend for 1,500 feet in front
of the holding aircraft starting at a point 375 feet from the departure threshold (see FIG 2−1−11). Illuminated red
lights provide a signal, to an aircraft in position for takeoff or rolling, that it is unsafe to takeoff because the
runway is occupied or about to be occupied by another aircraft or ground vehicle. Two aircraft, or a surface
vehicle and an aircraft, are required for the lights to illuminate. The departing aircraft must be in position for
takeoff or beginning takeoff roll. Another aircraft or a surface vehicle must be on or about to cross the runway.
1. THL Operating Characteristics − Departing Aircraft: THLs will illuminate for an aircraft in position for
departure or departing when there is another aircraft or vehicle on the runway or about to enter the runway (see
FIG 2−1−9.) Once that aircraft or vehicle exits the runway, the THLs extinguish. A pilot may notice lights
extinguish prior to the downfield aircraft or vehicle being completely clear of the runway but still moving. Like
RELs, THLs have an “anticipated separation” feature.
NOTE−
When the THLs extinguish, this is not clearance to begin a takeoff roll. All takeoff clearances will be issued by ATC.
2. What a pilot would observe: A pilot in position to depart from a runway, or has begun takeoff roll, will
observe THLs illuminate in reaction to an aircraft or vehicle on the runway or entering or crossing it. Lights will
extinguish when the runway is clear. A pilot may observe several cycles of illumination and extinguishing
depending on the amount of crossing traffic.
3. When a pilot observes the red light of the THLs, the pilot should safely stop if it’s feasible or remain
stopped. The pilot must contact ATC for resolution if any clearance is in conflict with the lights. Should pilots
note illuminated lights while in takeoff roll and under circumstances when stopping is impractical for safety
2−1−8 Airport Lighting Aids
2/20/25 AIM
reasons, the crew should proceed according to their best judgment while understanding the illuminated lights
indicate that continuing the takeoff is unsafe. Contact ATC at the earliest possible opportunity.
d. Pilot Actions:
1. When operating at airports with RWSL, pilots will operate with the transponder/ADS −B “On” when
departing the gate or parking area until it is shut down upon arrival at the gate or parking area. This ensures
interaction with the FAA surveillance systems such as ASDE-X/Airport Surface Surveillance Capability (ASSC)
which provide information to the RWSL system.
2. Pilots must always inform the ATCT when they have stopped due to an RWSL indication that is in conflict
with ATC instructions. Pilots must request clarification of the taxi or takeoff clearance.
3. Never cross over illuminated red lights. Under normal circumstances, RWSL will confirm the pilot’s taxi
or takeoff clearance previously issued by ATC. If RWSL indicates that it is unsafe to takeoff from, land on, cross,
or enter a runway, immediately notify ATC of the conflict and re-confirm the clearance.
4. Do not proceed when lights have extinguished without an ATC clearance. RWSL verifies an ATC
clearance; it does not substitute for an ATC clearance.
e. ATC Control of RWSL System:
1. Controllers can set in−pavement lights to one of five (5) brightness levels to assure maximum conspicuity
under all visibility and lighting conditions. REL and THL subsystems may be independently set.
2. System lights can be disabled should RWSL operations impact the efficient movement of air traffic or
contribute, in the opinion of the assigned ATC Manager, to unsafe operations. REL and THL light fixtures may
be disabled separately. Whenever the system or a component is disabled, a NOTAM must be issued, and the
Automatic Terminal Information System (ATIS) must be updated.
2−1−7. Control of Lighting Systems
a. Operation of approach light systems and runway lighting is controlled by the control tower (ATCT). At
some locations the FSS may control the lights where there is no control tower in operation.
b. Pilots may request that lights be turned on or off. Runway edge lights, in−pavement lights and approach
lights also have intensity controls which may be varied to meet the pilots request. Sequenced flashing lights
(SFL) may be turned on and off. Some sequenced flashing light systems also have intensity control.
2−1−8. Pilot Control of Airport Lighting
Radio control of lighting is available at selected airports to provide airborne control of lights by keying the
aircraft’s microphone. Control of lighting systems is often available at locations without specified hours for
lighting and where there is no control tower or FSS or when the tower or FSS is closed (locations with a part−time
tower or FSS) or specified hours. All lighting systems which are radio controlled at an airport, whether on a single
runway or multiple runways, operate on the same radio frequency. (See TBL 2−1−1 and TBL 2−1−2.)
Airport Lighting Aids 2−1−9
AIM 2/20/25
FIG 2−1−10
Runway Entrance Lights
FIG 2−1−11
Takeoff Hold Lights
2−1−10 Airport Lighting Aids
2/20/25 AIM
FIG 2−1−12
Taxiway Lead−On Light Configuration
TBL 2−1−1
Runways With Approach Lights
Lighting System No. of Int.
Steps
Status During
Nonuse Period
Intensity Step Selected Per No. of Mike Clicks
3 Clicks 5 Clicks 7 Clicks
Approach Lights (Med. Int.) 2 Off Low Low High
Approach Lights (Med. Int.) 3 Off Low Med High
MIRL 3 Off or Low
HIRL 5 Off or Low
V ASI 2 Off
NOTES: Predetermined intensity step.
Low intensity for night use. High intensity for day use as determined by photocell control.
TBL 2−1−2
Runways Without Approach Lights
Lighting System No. of Int.
Steps
Status During
Nonuse Period
Intensity Step Selected Per No. of Mike Clicks
3 Clicks 5 Clicks 7 Clicks
MIRL 3 Off or Low Low Med. High
HIRL 5 Off or Low Step 1 or 2 Step 3 Step 5
LIRL 1 Off On On On
V ASI 2 Off
REIL 1 Off Off On/Off On
REIL 3 Off Low Med. High
NOTES: Low intensity for night use. High intensity for day use as determined by photocell control.
The control of V ASI and/or REIL may be independent of other lighting systems.
Airport Lighting Aids 2−1−11
AIM 2/20/25
a. With FAA approved systems, various combinations of medium intensity approach lights, runway lights,
taxiway lights, V ASI and/or REIL may be activated by radio control. On runways with both approach lighting
and runway lighting (runway edge lights, taxiway lights, etc.) systems, the approach lighting system takes
precedence for air−to−ground radio control over the runway lighting system which is set at a predetermined
intensity step, based on expected visibility conditions. Runways without approach lighting may provide radio
controlled intensity adjustments of runway edge lights. Other lighting systems, including V ASI, REIL, and
taxiway lights may be either controlled with the runway edge lights or controlled independently of the runway
edge lights.
b. The control system consists of a 3−step control responsive to 7, 5, and/or 3 microphone clicks. This 3−step
control will turn on lighting facilities capable of either 3−step, 2−step or 1−step operation. The 3−step and 2−step
lighting facilities can be altered in intensity, while the 1−step cannot. All lighting is illuminated for a period of
15 minutes from the most recent time of activation and may not be extinguished prior to end of the 15 minute
period (except for 1−step and 2−step REILs which may be turned off when desired by keying the mike 5 or 3
times respectively).
c. Suggested use is to always initially key the mike 7 times; this assures that all controlled lights are turned
on to the maximum available intensity. If desired, adjustment can then be made, where the capability is provided,
to a lower intensity (or the REIL turned off) by keying 5 and/or 3 times. Due to the close proximity of airports
using the same frequency, radio controlled lighting receivers may be set at a low sensitivity requiring the aircraft
to be relatively close to activate the system. Consequently, even when lights are on, always key mike as directed
when overflying an airport of intended landing or just prior to entering the final segment of an approach. This
will assure the aircraft is close enough to activate the system and a full 15 minutes lighting duration is available.
Approved lighting systems may be activated by keying the mike (within 5 seconds) as indicated in TBL 2−1−3.
TBL 2−1−3
Radio Control System
Key Mike Function
7 times within 5 seconds Highest intensity available
5 times within 5 seconds Medium or lower intensity
(Lower REIL or REIL−off)
3 times within 5 seconds Lowest intensity available
(Lower REIL or REIL−off)
d. For all public use airports with FAA standard systems the Chart Supplement contains the types of lighting,
runway and the frequency that is used to activate the system. Airports with IAPs include data on the approach
chart identifying the light system, the runway on which they are installed, and the frequency that is used to
activate the system.
NOTE−
Although the CTAF is used to activate the lights at many airports, other frequencies may also be used. The appropriate
frequency for activating the lights on the airport is provided in the Chart Supplement and the standard instrument approach
procedures publications. It is not identified on the sectional charts.
e. Where the airport is not served by an IAP, it may have either the standard FAA approved control system
or an independent type system of different specification installed by the airport sponsor. The Chart Supplement
contains descriptions of pilot controlled lighting systems for each airport having other than FAA approved
systems, and explains the type lights, method of control, and operating frequency in clear text.
2−1−9. Airport/Heliport Beacons
a. Airport and heliport beacons have a vertical light distribution to make them most effective from one to ten
degrees above the horizon; however, they can be seen well above and below this peak spread. The beacon may
be an omnidirectional capacitor−discharge device, or it may rotate at a constant speed which produces the visual
effect of flashes at regular intervals. Flashes may be one or two colors alternately. The total number of flashes
are:
2−1−12 Airport Lighting Aids
2/20/25 AIM
1. 24 to 30 per minute for beacons marking airports, landmarks, and points on Federal airways.
2. 30 to 45 per minute for beacons marking heliports.
b. The colors and color combinations of beacons are:
1. White and Green− Lighted land airport.
2. *Green alone− Lighted land airport.
3. White and Yellow− Lighted water airport.
4. *Yellow alone− Lighted water airport.
5. Green, Yellow, and White− Lighted heliport.
NOTE−
*Green alone or yellow alone is used only in connection with a white −and−green or white−and−yellow beacon display,
respectively.
c. Military airport beacons flash alternately white and green, but are differentiated from civil beacons by
dualpeaked (two quick) white flashes between the green flashes.
d. In Class B, Class C, Class D and Class E surface areas, operation of the airport beacon during the hours
of daylight often indicates that the ground visibility is less than 3 miles and/or the ceiling is less than 1,000 feet.
ATC clearance in accordance with 14 CFR part 91 is required for landing, takeoff and flight in the traffic pattern.
Pilots should not rely solely on the operation of the airport beacon to indicate if weather conditions are IFR or
VFR. At some locations with operating control towers, ATC personnel turn the beacon on or off when controls
are in the tower. At many airports the airport beacon is turned on by a photoelectric cell or time clocks and ATC
personnel cannot control them. There is no regulatory requirement for daylight operation and it is the pilot’s
responsibility to comply with proper preflight planning as required by 14 CFR section 91.103.
2−1−10. Taxiway Lights
a. Taxiway Edge Lights. Taxiway edge lights are used to outline the edges of taxiways during periods of
darkness or restricted visibility conditions. These fixtures emit blue light.
NOTE−
At most major airports these lights have variable intensity settings and may be adjusted at pilot request or when deemed
necessary by the controller .
b. Taxiway Centerline Lights. Taxiway centerline lights are used to facilitate ground traffic under low
visibility conditions. They are located along the taxiway centerline in a straight line on straight portions, on the
centerline of curved portions, and along designated taxiing paths in portions of runways, ramp, and apron areas.
Taxiway centerline lights are steady burning and emit green light.
c. Clearance Bar Lights. Clearance bar lights are installed at holding positions on taxiways in order to
increase the conspicuity of the holding position in low visibility conditions. They may also be installed to indicate
the location of an intersecting taxiway during periods of darkness. Clearance bars consist of three in−pavement
steady−burning yellow lights.
d. Runway Guard Lights. Runway guard lights are installed at taxiway/runway intersections. They are
primarily used to enhance the conspicuity of taxiway/runway intersections during low visibility conditions, but
may be used in all weather conditions. Runway guard lights consist of either a pair of elevated flashing yellow
lights installed on either side of the taxiway, or a row of in−pavement yellow lights installed across the entire
taxiway, at the runway holding position marking.
NOTE−
Some airports may have a row of three or five in−pavement yellow lights installed at taxiway/runway intersections. They
should not be confused with clearance bar lights described in paragraph 2−1−10c, Clearance Bar Lights.
e. Stop Bar Lights. Stop bar lights, when installed, are used to confirm the ATC clearance to enter or cross
the active runway in low visibility conditions (below 1,200 ft Runway Visual Range). A stop bar consists of a
Airport Lighting Aids 2−1−13
AIM 2/20/25
row of red, unidirectional, steady−burning in−pavement lights installed across the entire taxiway at the runway
holding position, and elevated steady −burning red lights on each side. A controlled stop bar is operated in
conjunction with the taxiway centerline lead −on lights which extend from the stop bar toward the runway.
Following the ATC clearance to proceed, the stop bar is turned off and the lead−on lights are turned on. The stop
bar and lead−on lights are automatically reset by a sensor or backup timer.
CAUTION−
Pilots should never cross a red illuminated stop bar, even if an ATC clearance has been given to proceed onto or across
the runway.
NOTE−
If after crossing a stop bar, the taxiway centerline lead−on lights inadvertently extinguish, pilots should hold their position
and contact ATC for further instructions.
2−1−14 Airport Lighting Aids
2/20/25 AIM
Section 2. Air Navigation and Obstruction Lighting
2−2−1. Aeronautical Light Beacons
a. An aeronautical light beacon is a visual NA VAID displaying flashes of white and/or colored light to indicate
the location of an airport, a heliport, a landmark, a certain point of a Federal airway in mountainous terrain, or
an obstruction. The light used may be a rotating beacon or one or more flashing lights. The flashing lights may
be supplemented by steady burning lights of lesser intensity.
b. The color or color combination displayed by a particular beacon and/or its auxiliary lights tell whether the
beacon is indicating a landing place, landmark, point of the Federal airways, or an obstruction. Coded flashes
of the auxiliary lights, if employed, further identify the beacon site.
2−2−2. Code Beacons and Course Lights
a. Code Beacons. The code beacon, which can be seen from all directions, is used to identify airports and
landmarks. The code beacon flashes the three or four character airport identifier in International Morse Code six
to eight times per minute. Green flashes are displayed for land airports while yellow flashes indicate water
airports.
b. Course Lights. The course light, which can be seen clearly from only one direction, is used only with
rotating beacons of the Federal Airway System: two course lights, back to back, direct coded flashing beams of
light in either direction along the course of airway.
NOTE−
Airway beacons are remnants of the “lighted” airways which antedated the present electronically equipped federal airways
system. Only a few of these beacons exist today to mark airway segments in remote mountain areas. Flashes in Morse code
identify the beacon site.
2−2−3. Obstruction Lights
a. Obstructions are marked/lighted to warn airmen of their presence during daytime and nighttime conditions.
They may be marked/lighted in any of the following combinations:
1. Aviation Red Obstruction Lights. Flashing aviation red beacons (20 to 40 flashes per minute) and
steady burning aviation red lights during nighttime operation. Aviation orange and white paint is used for daytime
marking.
2. Medium Intensity Flashing White Obstruction Lights. Medium intensity flashing white obstruction
lights may be used during daytime and twilight with automatically selected reduced intensity for nighttime
operation. When this system is used on structures 500 feet (153m) AGL or less in height, other methods of
marking and lighting the structure may be omitted. Aviation orange and white paint is always required for
daytime marking on structures exceeding 500 feet (153m) AGL. This system is not normally installed on
structures less than 200 feet (61m) AGL.
3. High Intensity White Obstruction Lights. Flashing high intensity white lights during daytime with
reduced intensity for twilight and nighttime operation. When this type system is used, the marking of structures
with red obstruction lights and aviation orange and white paint may be omitted.
4. Dual Lighting. A combination of flashing aviation red beacons and steady burning aviation red lights
for nighttime operation and flashing high intensity white lights for daytime operation. Aviation orange and white
paint may be omitted.
5. Catenary Lighting. Lighted markers are available for increased night conspicuity of high −voltage
(69KV or higher) transmission line catenary wires. Lighted markers provide conspicuity both day and night.
Air Navigation and Obstruction Lighting 2−2−1
AIM 2/20/25
b. Medium intensity omnidirectional flashing white lighting system provides conspicuity both day and night
on catenary support structures. The unique sequential/simultaneous flashing light system alerts pilots of the
associated catenary wires.
c. High intensity flashing white lights are being used to identify some supporting structures of overhead
transmission lines located across rivers, chasms, gorges, etc. These lights flash in a middle, top, lower light
sequence at approximately 60 flashes per minute. The top light is normally installed near the top of the supporting
structure, while the lower light indicates the approximate lower portion of the wire span. The lights are beamed
towards the companion structure and identify the area of the wire span.
d. High intensity flashing white lights are also employed to identify tall structures, such as chimneys and
towers, as obstructions to air navigation. The lights provide a 360 degree coverage about the structure at 40
flashes per minute and consist of from one to seven levels of lights depending upon the height of the structure.
Where more than one level is used the vertical banks flash simultaneously.
2−2−4. LED Lighting Systems
Certain light− emitting diode (LED) lighting systems fall outside the combined visible and near −infrared
spectrum of night vision goggles (NVGs) and thus will not be visible to a flightcrew using NVGs.
The FAA changed specifications for LED −based red obstruction lights to make them visible to pilots using
certain NVG systems, however, other colors may not be visible.
It is recommended that air carriers/operators—includi ng part 91 operators—who use NVGs incorporate
procedures into manuals and/or standard operating procedures (SOPs) requiring periodic, unaided scanning
when operating at low altitudes and when performing a reconnaissance of landing areas.
2−2−2 Air Navigation and Obstruction Lighting
2/20/25 AIM
2−2−3
2/20/25 AIM
Section 3. Airport Marking Aids and Signs
2−3−1. General
a. Airport pavement markings and signs provide information that is useful to a pilot during takeoff, landing,
and taxiing.
b. Uniformity in airport markings and signs from one airport to another enhances safety and improves
efficiency. Pilots are encouraged to work with the operators of the airports they use to achieve the marking and
sign standards described in this section.
c. Pilots who encounter ineffective, incorrect, or confusing markings or signs on an airport should make the
operator of the airport aware of the problem. These situations may also be reported under the Aviation Safety
Reporting Program as described in paragraph 7−7−1, Aviation Safety Reporting Program. Pilots may also report
these situations to the FAA regional airports division.
d. The markings and signs described in this section of the AIM reflect the current FAA recommended
standards.
REFERENCE−
AC 150/5340−1, Standards for Airport Markings.
AC 150/5340−18, Standards for Airport Sign Systems.
2−3−2. Airport Pavement Markings
a. General. For the purpose of this section, the airport pavement markings have been grouped into four areas:
1. Runway Markings.
2. Taxiway Markings.
3. Holding Position Markings.
4. Other Markings.
b. Marking Colors. Markings for runways are white. Markings defining the landing area on a heliport are
also white except for hospital heliports which use a red “H” on a white cross. Markings for taxiways, areas not
intended for use by aircraft (closed and hazardous areas), and holding positions (even if they are on a runway)
are yellow.
2−3−3. Runway Markings
a. General. There are three types of markings for runways: visual, nonprecision instrument, and precision
instrument. TBL 2−3−1 identifies the marking elements for each type of runway and TBL 2 −3−2 identifies
runway threshold markings.
TBL 2−3−1
Runway Marking Elements
Marking Element Visual Runway
Nonprecision
Instrument
Runway
Precision
Instrument
Runway
Designation X X X
Centerline X X X
Threshold X1 X X
Aiming Point X2 X X
Touchdown Zone X
Side Stripes X
1 On runways used, or intended to be used, by international commercial transports.
2 On runways 4,000 feet (1200 m) or longer used by jet aircraft.
Airport Marking Aids and Signs 2−3−1
AIM 2/20/25
FIG 2−3−1
Precision Instrument Runway Markings
b. Runway Designators. Runway numbers and letters are determined from the approach direction. The
runway number is the whole number nearest one-tenth the magnetic azimuth of the centerline of the runway,
measured clockwise from the magnetic north. The letters, differentiate between left (L), right (R), or center (C)
parallel runways, as applicable:
1. For two parallel runways “L” “R.”
2. For three parallel runways “L” “C” “R.”
c. Runway Centerline Marking. The runway centerline identifies the center of the runway and provides
alignment guidance during takeoff and landings. The centerline consists of a line of uniformly spaced stripes and
gaps.
d. Runway Aiming Point Marking. The aiming point marking serves as a visual aiming point for a landing
aircraft. These two rectangular markings consist of a broad white stripe located on each side of the runway
centerline and approximately 1,000 feet from the landing threshold, as shown in FIG 2−3−1, Precision
Instrument Runway Markings.
e. Runway Touchdown Zone Markers. The touchdown zone markings identify the touchdown zone for
landing operations and are coded to provide distance information in 500 feet (150m) increments. These markings
consist of groups of one, two, and three rectangular bars symmetrically arranged in pairs about the runway
centerline, as shown in FIG 2−3−1. For runways having touchdown zone markings on both ends, those pairs of
markings which extend to within 900 feet (270 m) of the midpoint between the thresholds are eliminated.
2−3−2 Airport Marking Aids and Signs
20
20
2/20/25 AIM
FIG 2−3−2
Nonprecision Instrument Runway and Visual Runway Markings
AIMING POINT
MARKING
THRESHOLD THRESHOLD
MARKINGS
DESIGNATION
MARKING
PAVEMENT EDGE
AIMING POINT
MARKING
PAVEMENT EDGE
DESIGNATION MARKING
THRESHOLD
NONPRECISION INSTRUMENT RUNWAY MARKINGS
VISUAL RUNWAY MARKINGS
f. Runway Side Stripe Marking. Runway side stripes delineate the edges of the runway. They provide a
visual contrast between runway and the abutting terrain or shoulders. Side stripes consist of continuous white
stripes located on each side of the runway as shown in FIG 2−3−4.
g. Runway Shoulder Markings. Runway shoulder stripes may be used to supplement runway side stripes
to identify pavement areas contiguous to the runway sides that are not intended for use by aircraft. Runway
shoulder stripes are yellow. (See FIG 2−3−5.)
h. Runway Threshold Markings. Runway threshold markings come in two configurations. They either
consist of eight longitudinal stripes of uniform dimensions disposed symmetrically about the runway centerline
(as shown in FIG 2−3−1) or the number of stripes is related to the runway width as indicated in TBL 2−3−2. A
threshold marking helps identify the beginning of the runway that is available for landing. In some instances,
the landing threshold may be relocated or displaced.
TBL 2−3−2
Number of Runway Threshold Stripes
Runway Width Number of Stripes
60 feet (18 m) 4
75 feet (23 m) 6
100 feet (30 m) 8
150 feet (45 m) 12
200 feet (60 m) 16
Airport Marking Aids and Signs 2−3−3
AIM 2/20/25
1. Relocation of a Threshold. Sometimes construction, maintenance, or other activities require the
threshold to be relocated towards the rollout end of the runway. (See FIG 2−3−3.) When a threshold is relocated,
it closes not only a set portion of the approach end of a runway, but also shortens the length of the opposite
direction runway. In these cases, a NOTAM should be issued by the airport operator identifying the portion of
the runway that is closed (for example, 10/28 W 900 CLSD). Because the duration of the relocation can vary from
a few hours to several months, methods identifying the new threshold may vary. One common practice is to use
a ten feet wide white threshold bar across the width of the runway. Although the runway lights in the area between
the old threshold and new threshold will not be illuminated, the runway markings in this area may or may not
be obliterated, removed, or covered.
2. Displaced Threshold. A displaced threshold is a threshold located at a point on the runway other than
the designated beginning of the runway. Displacement of a threshold reduces the length of runway available for
landings. The portion of runway behind a displaced threshold is available for takeoffs in either direction and
landings from the opposite direction. A ten feet wide white threshold bar is located across the width of the runway
at the displaced threshold. White arrows are located along the centerline in the area between the beginning of
the runway and displaced threshold. White arrow heads are located across the width of the runway just prior to
the threshold bar, as shown in FIG 2−3−4.
NOTE−
Airport operator. When reporting the relocation or displacement of a threshold, the airport operator should avoid language
which confuses the two.
i. Demarcation Bar. A demarcation bar delineates a runway with a displaced threshold from a blast pad,
stopway, or taxiway that precedes the runway. A demarcation bar is 3 feet (1m) wide and yellow, since it is not
located on the runway, as shown in FIG 2−3−6.
1. Chevrons. These markings are used to show pavement areas aligned with the runway that are unusable
for landing, takeoff, and taxiing. Chevrons are yellow. (See FIG 2−3−7.)
j. Runway Threshold Bar. A threshold bar delineates the beginning of the runway that is available for
landing when the threshold has been relocated or displaced. A threshold bar is 10 feet (3m) in width and extends
across the width of the runway, as shown in FIG 2−3−4.
2−3−4 Airport Marking Aids and Signs
2/20/25 AIM
FIG 2−3−3
Relocation of a Threshold with Markings for Taxiway Aligned with Runway
Airport Marking Aids and Signs 2−3−5
AIM 2/20/25
FIG 2−3−4
Displaced Threshold Markings
2−3−6 Airport Marking Aids and Signs
2/20/25 AIM
FIG 2−3−5
Runway Shoulder Markings
RUNWAY THRESHOLD
MIDPOINT OF
RUNWAY
SHOULDER SHOULDERRUNWAY
45° 45°
45° 45°
2−3−4. Taxiway Markings
a. General. All taxiways should have centerline markings and runway holding position markings whenever
they intersect a runway. Taxiway edge markings are present whenever there is a need to separate the taxiway from
a pavement that is not intended for aircraft use or to delineate the edge of the taxiway. Taxiways may also have
shoulder markings and holding position markings for Instrument Landing System (ILS) critical areas and
taxiway/taxiway intersection markings.
REFERENCE−
AIM, Para 2−3−5, Holding Position Markings.
b. Taxiway Centerline.
1. Normal Centerline. The taxiway centerline is a single continuous yellow line, 6 inches (15 cm) to 12
inches (30 cm) in width. This provides a visual cue to permit taxiing along a designated path. Ideally, the aircraft
should be kept centered over this line during taxi. However, being centered on the taxiway centerline does not
guarantee wingtip clearance with other aircraft or other objects.
2. Enhanced Centerline. At some airports, mostly the larger commercial service airports, an enhanced
taxiway centerline will be used. The enhanced taxiway centerline marking consists of a parallel line of yellow
dashes on either side of the normal taxiway centerline. The taxiway centerlines are enhanced for a maximum of
150 feet prior to a runway holding position marking. The purpose of this enhancement is to warn the pilot that
he/she is approaching a runway holding position marking and should prepare to stop unless he/she has been
cleared onto or across the runway by ATC. (See FIG 2−3−8.)
c. Taxiway Edge Markings. Taxiway edge markings are used to define the edge of the taxiway. They are
primarily used when the taxiway edge does not correspond with the edge of the pavement. There are two types
of markings depending upon whether the aircraft is supposed to cross the taxiway edge:
Airport Marking Aids and Signs 2−3−7
AIM 2/20/25
1. Continuous Markings. These consist of a continuous double yellow line, with each line being at least
6 inches (15 cm) in width spaced 6 inches (15 cm) apart. They are used to define the taxiway edge from the
shoulder or some other abutting paved surface not intended for use by aircraft.
2. Dashed Markings. These markings are used when there is an operational need to define the edge of a
taxiway or taxilane on a paved surface where the adjoining pavement to the taxiway edge is intended for use by
aircraft (for example, an apron). Dashed taxiway edge markings consist of a broken double yellow line, with each
line being at least 6 inches (15 cm) in width, spaced 6 inches (15 cm) apart (edge to edge). These lines are 15
feet (4.5 m) in length with 25 foot (7.5 m) gaps. (See FIG 2−3−9.)
d. Taxi Shoulder Markings. Taxiways, holding bays, and aprons are sometimes provided with paved
shoulders to prevent blast and water erosion. Although shoulders may have the appearance of full strength
pavement, they are not intended for use by aircraft and may be unable to support an aircraft. Usually the taxiway
edge marking will define this area. Where conditions exist such as islands or taxiway curves that may cause
confusion as to which side of the edge stripe is for use by aircraft, taxiway shoulder markings may be used to
indicate the pavement is unusable. Taxiway shoulder markings are yellow. (See FIG 2−3−10.)
2−3−8 Airport Marking Aids and Signs
2/20/25 AIM
FIG 2−3−6
Markings for Blast Pad or Stopway or Taxiway Preceding a Displaced Threshold
Airport Marking Aids and Signs 2−3−9
AIM 2/20/25
FIG 2−3−7
Markings for Blast Pads and Stopways
2−3−10 Airport Marking Aids and Signs
2/20/25 AIM
FIG 2−3−8
Enhanced Taxiway Centerline
FIG 2−3−9
Dashed Markings
DOUBLE
YELLOW
LINES
TAXIWAY EDGE TAXIWAY EDGE
MARKINGS MARKINGS
CONTINUOUS DASHED
e. Surface Painted Taxiway Direction Signs. Surface painted taxiway direction signs have a yellow
background with a black inscription, and are provided when it is not possible to provide taxiway direction signs
at intersections, or when necessary to supplement such signs. These markings are located adjacent to the
centerline with signs indicating turns to the left being on the left side of the taxiway centerline, and signs
indicating turns to the right being on the right side of the centerline. (See FIG 2−3−11.)
Airport Marking Aids and Signs 2−3−11
AIM 2/20/25
FIG 2−3−10
Taxi Shoulder Markings
RUNWAY
YELLOW STRIPES
PAVEMENT EDGE
TAXIWAY EDGE
MARKINGS
f. Surface Painted Location Signs. Surface painted location signs have a black background with a yellow
inscription. When necessary, these markings are used to supplement location signs located along side the taxiway
and assist the pilot in confirming the designation of the taxiway on which the aircraft is located. These markings
are located on the right side of the centerline. (See FIG 2−3−11.)
g. Geographic Position Markings. These markings are located at points along low visibility taxi routes
designated in the airport’s Surface Movement Guidance Control System (SMGCS) plan. They are used to
identify the location of taxiing aircraft during low visibility operations. Low visibility operations are those that
occur when the runway visible range (RVR) is below 1200 feet (360m). They are positioned to the left of the
taxiway centerline in the direction of taxiing. (See FIG 2−3−12.) The geographic position marking is a circle
comprised of an outer black ring contiguous to a white ring with a pink circle in the middle. When installed on
asphalt or other dark-colored pavements, the white ring and the black ring are reversed (i.e., the white ring
becomes the outer ring and the black ring becomes the inner ring). It is designated with either a number or a
number and letter. The number corresponds to the consecutive position of the marking on the route.
Airport Marking Aids and Signs2−3−12
2/20/25 AIM
FIG 2−3−11
Surface Painted Signs
Airport Marking Aids and Signs 2−3−13
AIM 2/20/25
2−3−5. Holding Position Markings
a. Runway Holding Position Markings. For runways, these markings indicate where aircraft MUST STOP
when approaching a runway. They consist of four yellow lines, two solid and two dashed, spaced six or twelve
inches apart, and extending across the width of the taxiway or runway. The solid lines are always on the side
where the aircraft must hold. There are three locations where runway holding position markings are encountered.
1. Runway Holding Position Markings on Taxiways. These markings identify the locations on a taxiway
where aircraft MUST STOP when a clearance has not been issued to proceed onto the runway. Generally, runway
holding position markings also identify the boundary of the runway safety area (RSA) for aircraft exiting the
runway. Runway holding position markings are shown in FIG 2−3−13 and FIG 2−3−16. When instructed by
ATC, “Hold short of Runway XX,” the pilot MUST STOP so that no part of the aircraft extends beyond the runway
holding position marking. When approaching runways at airports with an operating control tower, pilots must
not cross the runway holding position marking without ATC clearance. Pilots approaching runways at airports
without an operating control tower must ensure adequate separation from other aircraft, vehicles, and pedestrians
prior to crossing the holding position markings. An aircraft exiting a runway is not clear of the runway until all
parts of the aircraft have crossed the applicable holding position marking.
NOTE−
Runway holding position markings identify the beginning of an RSA, and a pilot MUST STOP to get clearance before
crossing (at airports with operating control towers).
REFERENCE−
AIM, Para 4−3−21, Exiting the Runway After Landing.
2. Runway Holding Position Markings on Runways. These markings identify the locations on runways
where aircraft MUST STOP. These markings are located on runways used by ATC for Land And Hold Short
Operations (for example, see FIG 4−3−8) and Taxiing operations. For taxiing operations, the pilot MUST STOP
prior to the holding position markings unless explicitly authorized to cross by ATC. A sign with a white
inscription on a red background is located adjacent to these holding position markings. (See FIG 2−3−14.) The
holding position markings are placed on runways prior to the intersection with another runway, or some
designated point. Pilots receiving and accepting instructions “Cleared to land Runway XX, hold short of Runway
YY” from ATC must either exit Runway XX prior to the holding position markings, or stop at the holding position
markings prior to Runway YY . Otherwise, pilots are authorized to use the entire landing length of the runway
and disregard the holding position markings.
3. Holding Position Markings on Taxiways Located in Runway Approach Areas. These markings are
used at some airports where it is necessary to hold an aircraft on a taxiway located in the approach or departure
area of a runway so that the aircraft does not interfere with the operations on that runway. This marking is
collocated with the runway approach/departure area holding position sign. When specifically instructed by ATC,
“Hold short of Runway XX approach or Runway XX departure area,” the pilot MUST STOP so that no part of
the aircraft extends beyond the holding position marking. (See Subparagraph 2−3−8b2, Runway Approach Area
Holding Position Sign, and FIG 2−3−15.)
b. Holding Position Markings for Instrument Landing System (ILS). Holding position markings for ILS
critical areas consist of two yellow solid lines spaced two feet apart connected by pairs of solid lines spaced ten
feet apart extending across the width of the taxiway as shown. (See FIG 2−3−16.) A sign with an inscription in
white on a red background is located adjacent to these hold position markings. When instructed by ATC to hold
short of the ILS critical area, pilots MUST STOP so that no part of the aircraft extends beyond the holding
position marking. When approaching the holding position marking, pilots must not cross the marking without
ATC clearance. The ILS critical area is not clear until all parts of the aircraft have crossed the applicable holding
position marking.
REFERENCE−
AIM, Para 1−1−9, Instrument Landing System (ILS).
c. Holding Position Markings for Intersecting Taxiways Holding position markings for intersecting
taxiways consist of a single dashed line extending across the width of the taxiway as shown. (See FIG 2−3−17.)
2−3−14 Airport Marking Aids and Signs
2/20/25 AIM
They are located on taxiways where ATC holds aircraft short of a taxiway intersection. When instructed by ATC,
“Hold short of Taxiway XX,” the pilot MUST STOP so that no part of the aircraft extends beyond the holding
position marking. When the marking is not present, the pilot MUST STOP the aircraft at a point which provides
adequate clearance from an aircraft on the intersecting taxiway.
d. Surface Painted Holding Position Signs. Surface painted holding position signs have a red background
with a white inscription and supplement the signs located at the holding position. This type of marking is
normally used where the width of the holding position on the taxiway is greater than 200 feet (60 m). It is located
to the left side of the taxiway centerline on the holding side and prior to the holding position marking. (See
FIG 2−3−11.)
FIG 2−3−12
Geographic Position Markings
Airport Marking Aids and Signs 2−3−15
AIM 2/20/25
FIG 2−3−13
Runway Holding Position Markings on Taxiway
15
RUNWAY TAXIWAY/RUNWAY
HOLDING POSITION
MARKINGS
HOLDING
BAY TAXIWAY
EXAMPLE OF HOLDING POSITION MARKINGS
EXTENDED ACROSS HOLDING BAY
Airport Marking Aids and Signs2−3−16
2/20/25 AIM
FIG 2−3−14
Runway Holding Position Markings on Runways
Airport Marking Aids and Signs 2−3−17
AIM 2/20/25
FIG 2−3−15
Taxiways Located in Runway Approach and Departure Areas
2−3−18 Airport Marking Aids and Signs
2/20/25 AIM
NOTE−
1. Refer to Advisory Circular 150/5300−13 for additional information on obstruction surfaces.
2. Because Taxiway C does not enter the departure area of Runway 33, the sign on Taxiway C does not include the “33 DEP”
legend.
3. The location of a holding position is relative to the point on the aircraft that infringes the surface; for inclining surfaces
such as an approach surface, the location of the holdline position may differ from the location of the infringement point.
FIG 2−3−16
Holding Position Markings: ILS Critical Area
2−3−6. Other Markings
a. Vehicle Roadway Markings. The vehicle roadway markings are used when necessary to define a pathway
for vehicle operations on or crossing areas that are also intended for aircraft. These markings consist of a white
solid line to delineate each edge of the roadway and a dashed line to separate lanes within the edges of the
roadway. In lieu of the solid lines, zipper markings may be used to delineate the edges of the vehicle roadway.
(See FIG 2−3−18.) Details of the zipper markings are shown in FIG 2−3−19.
b. VOR Receiver Checkpoint Markings. The VOR receiver checkpoint marking allows the pilot to check
aircraft instruments with navigational aid signals. It consists of a painted circle with an arrow in the middle; the
arrow is aligned in the direction of the checkpoint azimuth. This marking, and an associated sign, is located on
Airport Marking Aids and Signs 2−3−19
AIM 2/20/25
the airport apron or taxiway at a point selected for easy access by aircraft but where other airport traffic is not
to be unduly obstructed. (See FIG 2−3−20.)
NOTE−
The associated sign contains the VOR station identification letter and course selected (published) for the check, the words
“VOR check course,” and DME data (when applicable). The color of the letters and numerals are black on a yellow
background.
EXAMPLE−
DCA 176−356
VOR check course
DME XXX
FIG 2−3−17
Holding Position Markings: Taxiway/Taxiway Intersections
TAXIWAY HOLDING
POSITION MARKINGS,
YELLOW, SEE
DETAIL 1
DETAIL 1
2−3−20 Airport Marking Aids and Signs
2/20/25 AIM
FIG 2−3−18
Vehicle Roadway Markings
Airport Marking Aids and Signs 2−3−21
AIM 2/20/25
FIG 2−3−19
Roadway Edge Stripes, White, Zipper Style
c. Nonmovement Area Boundary Markings. These markings delineate the movement area (i.e., area under
ATC). These markings are yellow and located on the boundary between the movement and nonmovement area.
The nonmovement area boundary markings consist of two yellow lines (one solid and one dashed) 6 inches
(15cm) in width. The solid line is located on the nonmovement area side, while the dashed yellow line is located
on the movement area side. The nonmovement boundary marking area is shown in FIG 2−3−21.
2−3−22 Airport Marking Aids and Signs
2/20/25 AIM
FIG 2−3−20
Ground Receiver Checkpoint Markings
1. WHITE
2. YELLOW
3. YELLOW ARROW ALIGNED TOWARD THE FACILITY
4. INTERIOR OF CIRCLE BLACK (CONCRETE SURFACE ONLY)
5. CIRCLE MAY BE BORDERED ON INSIDE AND OUTSIDE WITH
6" BLACK BAND IF NECESSARY FOR CONTRAST
1
4
2
3
5
2
FIG 2−3−21
Nonmovement Area Boundary Markings
DASHED LINE ON
MOVEMENT SIDE BOTH LINES
ARE YELLOW
SOLID LINE ON
NONMOVEMENT
SIDE
FIG 2−3−22
Closed or Temporarily Closed Runway and Taxiway Markings
X
d. Marking and Lighting of Permanently Closed Runways and Taxiways. For runways and taxiways
which are permanently closed, the lighting circuits will be disconnected. The runway threshold, runway
designation, and touchdown markings are obliterated and yellow crosses are placed at each end of the runway
and at 1,000 foot intervals. (See FIG 2−3−22.)
Airport Marking Aids and Signs 2−3−23
AIM 2/20/25
FIG 2−3−23
Helicopter Landing Areas
e. Temporarily Closed Runways and Taxiways. To provide a visual indication to pilots that a runway is
temporarily closed, crosses are placed on the runway only at each end of the runway. The crosses are yellow in
color. (See FIG 2−3−22.)
1. A raised lighted yellow cross may be placed on each runway end in lieu of the markings described in
Subparagraph e,Temporarily Closed Runways and Taxiways, to indicate the runway is closed.
2. A visual indication may not be present depending on the reason for the closure, duration of the closure,
airfield configuration, and the existence and the hours of operation of an airport traffic control tower. Pilots
should check NOTAMs and the Automated Terminal Information System (ATIS) for local runway and taxiway
closure information.
3. Temporarily closed taxiways are usually treated as hazardous areas, in which no part of an aircraft may
enter, and are blocked with barricades. However, as an alternative, a yellow cross may be installed at each
entrance to the taxiway.
f. Helicopter Landing Areas. The markings illustrated in FIG 2−3−23 are used to identify the landing and
takeoff area at a public use heliport and hospital heliport. The letter “H” in the markings is oriented to align with
the intended direction of approach. FIG 2−3−23 also depicts the markings for a closed airport.
2−3−7. Airport Signs
There are six types of signs installed on airfields: mandatory instruction signs, location signs, direction signs,
destination signs, information signs, and runway distance remaining signs. The characteristics and use of these
signs are discussed in paragraph 2 −3−8, Mandatory Instruction Signs, through paragraph 2 −3−13, Runway
Distance Remaining Signs.
REFERENCE−
AC150/5340−18, Standards for Airport Sign Systems for Detailed Information on Airport Signs.
2−3−24 Airport Marking Aids and Signs
2/20/25 AIM
FIG 2−3−24
Runway Holding Position Sign
FIG 2−3−25
Holding Position Sign at Beginning of Takeoff Runway
2−3−8. Mandatory Instruction Signs
a. These signs have a red background with a white inscription and are used to denote:
1. An entrance to a runway or critical area; and
2. Areas where an aircraft is prohibited from entering.
b. Typical mandatory signs and applications are:
1. Runway Holding Position Sign. This sign is located at the holding position on taxiways that intersect
a runway or on runways that intersect other runways. The inscription on the sign contains the designation of the
intersecting runway, as shown in FIG 2−3−24. The runway numbers on the sign are arranged to correspond to
the respective runway threshold. For example, “15−33” indicates that the threshold for Runway 15 is to the left
and the threshold for Runway 33 is to the right.
(a) On taxiways that intersect the beginning of the takeoff runway, only the designation of the takeoff
runway may appear on the sign (as shown in FIG 2−3−25), while all other signs will have the designation of both
runway directions.
Airport Marking Aids and Signs 2−3−25
AIM 2/20/25
FIG 2−3−26
Holding Position Sign for a Taxiway that Intersects the Intersection of Two Runways
FIG 2−3−27
Holding Position Sign for Runway Approach and Departure Areas
(b) If the sign is located on a taxiway that intersects the intersection of two runways, the designations for
both runways will be shown on the sign along with arrows showing the approximate alignment of each runway,
as shown in FIG 2−3−26. In addition to showing the approximate runway alignment, the arrow indicates the
direction to the threshold of the runway whose designation is immediately next to the arrow.
(c) A runway holding position sign on a taxiway will be installed adjacent to holding position markings
on the taxiway pavement. On runways, holding position markings will be located only on the runway pavement
adjacent to the sign, if the runway is normally used by ATC for “Land, Hold Short” operations or as a taxiway.
The holding position markings are described in paragraph 2−3−5, Holding Position Markings.
2. Runway Approach Area Holding Position Sign. At some airports, it is necessary to hold an aircraft
on a taxiway located in the approach or departure area for a runway so that the aircraft does not interfere with
operations on that runway. FIG 2−3−15 depicts common situations. A sign with the runway designation(s) and
the protected area(s) will be located at applicable holding positions on the taxiway. For locations protecting only
the approach area, the holding position on the taxiway includes a sign identifying the approach end runway
designation (e.g., 15) followed by a dash (−) and the letters “APCH”. For locations protecting both the approach
and departure areas, the holding position on the taxiway includes a sign with the approach end runway
2−3−26 Airport Marking Aids and Signs
2/20/25 AIM
designation and letters “APCH” followed by a dash (−), the departure end runway designation and the letters
“DEP”. The arrangement of the runway designations and protected areas legend on the sign reflects the
orientation of the runway as viewed from the holding position. Holding position markings in accordance with
paragraph 2−3−5, Holding Position Markings, are co−located on the taxiway pavement in line with the sign.
Examples of these signs are shown in FIG 2−3−27.
FIG 2−3−28
Holding Position Sign for ILS Critical Area
FIG 2−3−29
Sign Prohibiting Aircraft Entry into an Area
3. ILS Critical Area Holding Position Sign. At some airports, when the instrument landing system is
being used, it is necessary to hold an aircraft on a taxiway at a location other than the holding position described
in Paragraph 2 −3−5, Holding Position Markings. In these situ ations, the holding position sign for these
operations will have the inscription “ILS” and be located adjacent to the holding position marking on the taxiway
described in paragraph 2−3−5. An example of this sign is shown in FIG 2−3−28.
4. No Entry Sign. This sign, shown in FIG 2−3−29, prohibits an aircraft from entering an area. Typically,
this sign would be located on a taxiway intended to be used in only one direction or at the intersection of vehicle
roadways with runways, taxiways, or aprons where the roadway may be mistaken as a taxiway or other aircraft
movement surface.
NOTE−
Holding position signs provide the pilot with a visual cue as to the location of the holding position marking.
REFERENCE−
AIM, Para 2−3−5, Holding Position Markings.
Airport Marking Aids and Signs 2−3−27
AIM 2/20/25
FIG 2−3−30
Taxiway Location Sign
FIG 2−3−31
Taxiway Location Sign Collocated with Runway Holding Position Sign
2−3−9. Location Signs
a. Location signs are used to identify either a taxiway or runway on which the aircraft is located. Other location
signs provide a visual cue to pilots to assist them in determining when they have exited an area. The various
location signs are described below.
1. Taxiway Location Sign. This sign has a black background with a yellow inscription and yellow border,
as shown in FIG 2−3−30. The inscription is the designation of the taxiway on which the aircraft is located. These
signs are installed along taxiways either by themselves or in conjunction with direction signs or runway holding
position signs. (See FIG 2−3−35 and FIG 2−3−31.)
2−3−28 Airport Marking Aids and Signs
2/20/25 AIM
FIG 2−3−32
Runway Location Sign
FIG 2−3−33
Runway Boundary Sign
2. Runway Location Sign. This sign has a black background with a yellow inscription and yellow border,
as shown in FIG 2−3−32. The inscription is the designation of the runway on which the aircraft is located. These
signs are intended to complement the information available to pilots through their magnetic compass and
typically are installed where the proximity of two or more runways to one another could cause pilots to be
confused as to which runway they are on.
3. Runway Boundary Sign. This sign has a yellow background with a black inscription with a graphic
depicting the pavement holding position marking, as shown in FIG 2−3−33. This sign, which faces the runway
and is visible to the pilot exiting the runway, is located adjacent to the holding position marking on the pavement.
The sign is intended to provide pilots with another visual cue which they can use as a guide in deciding when
they are “clear of the runway.”
Airport Marking Aids and Signs 2−3−29
AIM 2/20/25
FIG 2−3−34
ILS Critical Area Boundary Sign
4. ILS Critical Area Boundary Sign. This sign has a yellow background with a black inscription with a
graphic depicting the ILS pavement holding position marking as shown in FIG 2−3−34. This sign is located
adjacent to the ILS holding position marking on the pavement and can be seen by pilots leaving the critical area.
The sign is intended to provide pilots with another visual cue which they can use as a guide in deciding when
they are “clear of the ILS critical area.”
2−3−10. Direction Signs
a. Direction signs have a yellow background with a black inscription. The inscription identifies the
designation(s) of the intersecting taxiway(s) leading out of the intersection that a pilot would normally be
expected to turn onto or hold short of. Each designation is accompanied by an arrow indicating the direction of
the turn.
b. Except as noted in subparagraph e, each taxiway designation shown on the sign is accompanied by only
one arrow. When more than one taxiway designation is shown on the sign, each designation and its associated
arrow is separated from the other taxiway designations by either a vertical message divider or a taxiway location
sign as shown in FIG 2−3−35.
c. Direction signs are normally located on the left prior to the intersection. When used on a runway to indicate
an exit, the sign is located on the same side of the runway as the exit. FIG 2−3−36 shows a direction sign used
to indicate a runway exit.
d. The taxiway designations and their associated arrows on the sign are arranged clockwise starting from the
first taxiway on the pilot’s left. (See FIG 2−3−35.)
e. If a location sign is located with the direction signs, it is placed so that the designations for all turns to the
left will be to the left of the location sign; the designations for continuing straight ahead or for all turns to the
right would be located to the right of the location sign. (See FIG 2−3−35.)
f. When the intersection is comprised of only one crossing taxiway, it is permissible to have two arrows
associated with the crossing taxiway, as shown in FIG 2−3−37. In this case, the location sign is located to the left
of the direction sign.
2−3−30 Airport Marking Aids and Signs
2/20/25 AIM
FIG 2−3−35
Direction Sign Array with Location Sign on Far Side of Intersection
FIG 2−3−36
Direction Sign for Runway Exit
Airport Marking Aids and Signs 2−3−31
AIM 2/20/253/15/077110.65R CHG 2AIM 8/7/25
FIG 2−3−37
Direction Sign Array for Simple Intersection
2−3−11. Destination Signs
a. Destination signs have a yellow background with a black inscription indicating a taxi route to a destination
on the airport. These signs supplement standard taxiway direction signs to optimize taxi paths to specific areas
of the airport.
b. Destination signs always have an arrow showing the direction of the taxi route to the destination indicated
on the sign. Where the destination sign arrow indicates a turn, the sign location is prior to the intersection. The
sign may reside on the opposite side of an inters ection for straight ahead paths and for ending taxiway
intersections.
c. Inbound destination signs identify a taxi path to specific areas of the airport. Sign legends are typically short
descriptions or abbreviations of the destination. FIG 2−3−38 shows examples of typical inbound destination
signs. Common sign legends include:
1. APRON. General parking, servicing, and loading areas
(a) FBO Apron. An apron where itinerant general aviation operators can park their aircraft and expect
to have access to traditional Fixed Base Operator services subject to terms and conditions.
(b) GA Transient Apron. An apron where itinerant general aviation operators can park their aircraft
without FBO services and subject to terms and conditions.
(c) GA Tenant Apron. An area designated for parking of based general aviation aircraft, e.g., tie down
area.
(d) North/South/East/West Apron. An apron designation describing relative location on the airport.
2. CARGO. Areas set aside for cargo handling.
2−3−32 Airport Marking Aids and Signs
AIM2/20/258/7/25 AIM
3. CIVIL. Areas set aside for civil aircraft.
4. FUEL. Areas where aircraft receive fuel or related services.
5. INTL. Areas set aside for handling international flights.
6. MIL. Areas set aside for military aircraft.
(a) ANG. Area reserved for Air National Guard
(b) USN. Area reserved for U.S. Navy
7. PARKING. Alternative name for apron area.
8. PAX. Areas set aside for passenger handling.
9. RAMP. Name synonymous with APRON.
10. TERM. Gate positions at which aircraft load or unload passengers and cargo.
d. Outbound destination signs identify the general direction to departure runways. The sign legend consists
of direction arrow(s) and the applicable runway designations. FIG 2−3−39 is an example of a typical outbound
destination sign.
e. When a sign indicates the inscription for two or more destinations having a common taxi route, a “dot” (•)
separates the destinations and one arrow indicates the direction of the taxi path, as shown in FIG 2−3−39.
f. When a sign shows the inscription for two or more destinations having different taxiing routes, each
destination will have its own arrow to indicate the taxi direction. A vertical black message divider separates each
destination, as shown in FIG 2−3−40.
Airport Marking Aids and Signs 2−3−33
AIM 2/20/253/15/077110.65R CHG 2AIM 8/7/25
FIG 2−3−38
Inbound Destination Sign Example
FIG 2−3−39
Outbound Destination Sign for Common Taxi Route to Two Separate Runways
2−3−34 Airport Marking Aids and Signs
AIM2/20/258/7/25 AIM
FIG 2−3−40
Destination Sign for Different Taxiing Routes to Two Runways
2−3−12. Information Signs
Information signs have a yellow background with a black inscription. They are used to provide the pilot with
information on such things as areas that cannot be seen from the control tower, applicable radio frequencies, and
noise abatement procedures. The airport operator determines the need, size, and location for these signs.
2−3−13. Runway Distance Remaining Signs
Runway distance remaining signs have a black background with a white numeral inscription and may be installed
along one or both side(s) of the runway. The number on the signs indicates the distance (in thousands of feet)
of landing runway remaining. The last sign (i.e., the sign with the numeral “1”) will be located at least 950 feet
from the runway end. FIG 2−3−41 shows an example of a runway distance remaining sign.
FIG 2−3−41
Runway Distance Remaining Sign Indicating 3,000 feet of Runway Remaining
3
2−3−14. Aircraft Arresting Systems
a. Certain airports are equipped with a means of rapidly stopping military aircraft on a runway. This
equipment, normally referred to as EMERGENCY ARRESTING GEAR, generally consists of pendant cables
Airport Marking Aids and Signs 2−3−35
AIM 2/20/253/15/077110.65R CHG 2AIM 8/7/25
supported over the runway surface by rubber “donuts.” Although most devices are located in the overrun areas,
a few of these arresting systems have cables stretched over the operational areas near the ends of a runway.
b. Arresting cables which cross over a runway require special markings on the runway to identify the cable
location. These markings consist of 10 feet diameter solid circles painted “identification yellow,” 30 feet on
center, perpendicular to the runway centerline across the entire runway width. Additional details are contained
in AC 150/5220−9, Aircraft Arresting Systems for Joint Civil/Military Airports.
NOTE−
Aircraft operations on the runway are not restricted by the installation of aircraft arresting devices.
c. Engineered Materials Arresting Systems (EMAS) . EMAS, which is constructed of high
energy−absorbing materials of selected strength, is located in the safety area beyond the end of the runway.
EMAS will be marked with yellow chevrons. EMAS is designed to crush under the weight of commercial aircraft
and will exert deceleration forces on the landing gear. These systems do not affect the normal landing and takeoff
of airplanes. More information concerning EMAS is in AC 150/5220−22, Engineered Materials Arresting
Systems (EMAS) for Aircraft Overruns.
NOTE−
EMAS may be located as close as 35 feet beyond the end of the runway. Aircraft and ground vehicles should never taxi or
drive across the EMAS or beyond the end of the runway if EMAS is present.
FIG 2−3−42
Engineered Materials Arresting System (EMAS)
2−3−15. Security Identification Display Area (SIDA)
a. Security Identification Display Areas (SIDA) are limited access areas that require a badge issued in
accordance with procedures in 49 CFR part 1542. A SIDA can include the Air Operations Area (AOA), e.g.,
aircraft movement area or parking area, or a Secured Area, such as where commercial passengers enplane. The
AOA may not be a SIDA, but a Secured Area is always a SIDA. Movement through or into a SIDA is prohibited
without authorization and proper identification being displayed. If you are unsure of the location of a SIDA,
contact the airport authority for additional information. Airports that have a SIDA will have a description and
map detailing boundaries and pertinent features available.
2−3−36 Airport Marking Aids and Signs
AIM2/20/258/7/25 AIM
b. Pilots or passengers without proper identification that are observed entering a SIDA may be reported to the
Transportation Security Administration (TSA) or airport security and may be subject to civil and criminal fines
and prosecution. Pilots are advised to brief passengers accordingly. Report suspicious activity to the TSA by
calling AOPA’s Airport Watch Program, 866−427−3287. 49 CFR 1540 requires each individual who holds an
airman certificate, medical certificate, authorization, or license issued by the FAA to present it for inspection
upon a request from TSA.
FIG 2−3−43
Sample SIDA Warning Sign
Airport Marking Aids and Signs 2−3−37
2/20/25 AIM
Chapter 3. Airspace
Section 1. General
3−1−1. General
a. There are two categories of airspace or airspace areas:
1. Regulatory (Class A, B, C, D and E airspace areas, restricted and prohibited areas); and
2. Nonregulatory (military operations areas [MOA], warning areas, alert areas, controlled firing areas
[CFA], and national security areas [NSA]).
NOTE−
Additional information on special use airspace (prohibited areas, restricted areas [permanent or temporary], warning
areas, MOAs [permanent or temporary], alert areas, CF As, and NSAs) may be found in Chapter 3, Airspace, Section 4,
Special Use Airspace, paragraphs 3−4−1 through 3−4−8.
b. Within these two categories, there are four types:
1. Controlled,
2. Uncontrolled,
3. Special use, and
4. Other airspace.
c. The categories and types of airspace are dictated by:
1. The complexity or density of aircraft movements,
2. The nature of the operations conducted within the airspace,
3. The level of safety required, and
4. The national and public interest.
d. It is important that pilots be familiar with the operational requirements for each of the various types or
classes of airspace. Subsequent sections will cover each class in sufficient detail to facilitate understanding.
3−1−2. General Dimensions of Airspace Segments
Refer to Title 14 of the U.S. Code of Federal Re gulations (CFR) for specific dimensions, exceptions,
geographical areas covered, exclusions, specific transponder/ADS −B or other equipment requirements, and
flight operations.
3−1−3. Hierarchy of Overlapping Airspace Designations
a. When overlapping airspace designations apply to the same airspace, the operating rules associated with the
more restrictive airspace designation apply.
b. For the purpose of clarification:
1. Class A airspace is more restrictive than Class B, Class C, Class D, Class E, or Class G airspace;
2. Class B airspace is more restrictive than Class C, Class D, Class E, or Class G airspace;
3. Class C airspace is more restrictive than Class D, Class E, or Class G airspace;
4. Class D airspace is more restrictive than Class E or Class G airspace; and
General 3−1−1
AIM 2/20/25
5. Class E is more restrictive than Class G airspace.
3−1−4. Basic VFR Weather Minimums
a. No person may operate an aircraft under basic VFR when the flight visibility is less, or at a distance from
clouds that is less, than that prescribed for the corresponding altitude and class of airspace. (See TBL 3−1−1.)
NOTE−
Student pilots must comply with 14 CFR section 61.89(a) (6) and (7).
b. Except as provided in 14 CFR section 91.157, Special VFR Weather Minimums, no person may operate
an aircraft beneath the ceiling under VFR within the lateral boundaries of controlled airspace designated to the
surface for an airport when the ceiling is less than 1,000 feet. (See 14 CFR section 91.155(c).)
TBL 3−1−1
Basic VFR Weather Minimums
Airspace Flight Visibility Distance from Clouds
Class A ........................................ Not Applicable Not Applicable
Class B ........................................ 3 statute miles Clear of Clouds
Class C ........................................ 3 statute miles 500 feet below
1,000 feet above
2,000 feet horizontal
Class D ........................................ 3 statute miles 500 feet below
1,000 feet above
2,000 feet horizontal
Class E
Less than 10,000 feet MSL ........................ 3 statute miles 500 feet below
1,000 feet above
2,000 feet horizontal
At or above 10,000 feet MSL ...................... 5 statute miles 1,000 feet below
1,000 feet above
1 statute mile horizontal
Class G
1,200 feet or less above the surface (regardless of MSL
altitude).
For aircraft other than helicopters:
Day, except as provided in §91.155(b) ............... 1 statute mile Clear of clouds
Night, except as provided in §91.155(b) ..............
For helicopters:
3 statute miles 500 feet below
1,000 feet above
2,000 feet horizontal
D a y ........................................... ½ statute mile Clear of clouds
Night, except as provided in §91.155(b) ..............
More than 1,200 feet above the surface but less than
10,000 feet MSL.
1 statute mile Clear of clouds
D a y ........................................... 1 statute mile 500 feet below
1,000 feet above
2,000 feet horizontal
Night ......................................... 3 statute miles 500 feet below
1,000 feet above
2,000 feet horizontal
More than 1,200 feet above the surface and at or above
10,000 feet MSL. ................................
5 statute miles 1,000 feet below
1,000 feet above
1 statute mile horizontal
General3−1−2
2/20/25 AIM
3−1−5. VFR Cruising Altitudes and Flight Levels
(See TBL 3−1−2.)
TBL 3−1−2
VFR Cruising Altitudes and Flight Levels
If your magnetic course
(ground track) is:
And you are more than 3,000 feet above the
surface but below 18,000 feet MSL, fly:
And you are above 18,000 feet
MSL to FL 290, fly:
0 to 179 . . . . ............ Odd thousands MSL, plus 500 feet
(3,500; 5,500; 7,500, etc.)
Odd Flight Levels plus 500 feet
(FL 195; FL 215; FL 235, etc.)
180 to 359 . ............. Even thousands MSL, plus 500 feet
(4,500; 6,500; 8,500, etc.)
Even Flight Levels plus 500 feet
(FL 185; FL 205; FL 225, etc.)
General 3−1−3
2/20/25 AIM
Section 2. Controlled Airspace
3−2−1. General
a. Controlled Airspace. A generic term that covers the different classification of airspace (Class A, Class B,
Class C, Class D, and Class E airspace) and defined dimensions within which air traffic control service is
provided to IFR flights and to VFR flights in accordance with the airspace classification. (See FIG 3−2−1.)
b. IFR Requirements. IFR operations in any class of controlled airspace requires that a pilot must file an
IFR flight plan and receive an appropriate ATC clearance.
c. IFR Separation. Standard IFR separation is provided to all aircraft operating under IFR in controlled
airspace.
d. VFR Requirements. It is the responsibility of the pilot to ensure that ATC clearance or radio
communication requirements are met prior to entry into Class B, Class C, or Class D airspace. The pilot retains
this responsibility when receiving ATC radar advisories. (See 14 CFR part 91.)
e. Traffic Advisories. Traffic advisories will be provided to all aircraft as the controller’s work situation
permits.
f. Safety Alerts. Safety Alerts are mandatory services and are provided to ALL aircraft. There are two types
of Safety Alerts:
1. Terrain/Obstruction Alert. A Terrain/Obstruction Alert is issued when, in the controller’s judgment,
an aircraft’s altitude places it in unsafe proximity to terrain and/or obstructions; and
2. Aircraft Conflict/Mode C Intruder Alert. An Aircraft Conflict/Mode C Intruder Alert is issued if the
controller observes another aircraft which places it in an unsafe proximity. When feasible, the controller will offer
the pilot an alternative course of action.
FIG 3−2−1
Airspace Classes
g. Ultralight V ehicles. No person may operate an ultralight vehicle within Class A, Class B, Class C, or Class
D airspace or within the lateral boundaries of the surface area of Class E airspace designated for an airport unless
that person has prior authorization from the ATC facility having jurisdiction over that airspace. (See 14 CFR part
103.)
h. Unmanned Free Balloons. Unless otherwise authorized by ATC, no person may operate an unmanned
free balloon below 2,000 feet above the surface within the lateral boundaries of Class B, Class C, Class D, or
Class E airspace designated for an airport. (See 14 CFR part 101.)
Controlled Airspace 3−2−1
AIM 2/20/25
i. Parachute Jumps. No person may make a parachute jump, and no pilot −in−command may allow a
parachute jump to be made from that aircraft, in or into Class A, Class B, Class C, or Class D airspace without,
or in violation of, the terms of an ATC authorization issued by the ATC facility having jurisdiction over the
airspace. (See 14 CFR part 105.)
3−2−2. Class A Airspace
a. Definition. Generally, that airspace from 18,000 feet MSL up to and including FL 600, including the
airspace overlying the waters within 12 nautical miles off the coast of the 48 contiguous States and Alaska; and
designated international airspace beyond 12 nautical miles off the coast of the 48 contiguous States and Alaska
within areas of domestic radio navigational signal or ATC radar coverage, and within which domestic procedures
are applied.
b. Operating Rules and Pilot/Equipment Requirements. Unless otherwise authorized, all persons must
operate their aircraft under IFR. (See 14 CFR section 71.33, sections 91.167 through 91.193, sections 91.215
through 91.217, and sections 91.225 through 91.227.)
c. Charts. Class A airspace is not specifically charted.
3−2−3. Class B Airspace
a. Definition. Generally, that airspace from the surface to 10,000 feet MSL surrounding the nation’s busiest
airports in terms of IFR operations or passenger enplanements. The configuration of each Class B airspace area
is individually tailored and consists of a surface area and two or more layers (some Class B airspace areas
resemble upside-down wedding cakes), and is designed to contain all published instrument procedures once an
aircraft enters the airspace. An ATC clearance is required for all aircraft to operate in the area, and all aircraft
that are so cleared receive separation services within the airspace. The cloud clearance requirement for VFR
operations is “clear of clouds.”
b. Operating Rules and Pilot/Equipment Requirements. Regardless of weather conditions, an ATC
clearance is required prior to operating within Class B airspace. Pilots should not request a clearance to operate
within Class B airspace unless the requirements of 14 CFR sections 91.131, 91.215, and 91.225 are met. Included
among these requirements are:
1. Unless otherwise authorized by ATC, aircraft must be equipped with an operable two-way radio capable
of communicating with ATC on appropriate frequencies for that Class B airspace.
2. No person may take off or land a civil aircraft at the following primary airports within Class B airspace
unless the pilot−in−command holds at least a private pilot certificate:
(a) Andrews Air Force Base, MD
(b) Atlanta Hartsfield Airport, GA
(c) Boston Logan Airport, MA
(d) Chicago O’Hare Intl. Airport, IL
(e) Dallas/Fort Worth Intl. Airport, TX
(f) Los Angeles Intl. Airport, CA
(g) Miami Intl. Airport, FL
(h) Newark Intl. Airport, NJ
(i) New York Kennedy Airport, NY
(j) New York La Guardia Airport, NY
(k) Ronald Reagan Washington National Airport, DC
3−2−2 Controlled Airspace
2/20/25 AIM
(l) San Francisco Intl. Airport, CA
3. No person may take off or land a civil aircraft at an airport within Class B airspace or operate a civil
aircraft within Class B airspace unless:
(a) The pilot−in−command holds at least a private pilot certificate; or
(b) The pilot−in−command holds a recreational pilot certificate and has met the requirements of 14 CFR
section 61.101; or
(c) The pilot−in−command holds a sport pilot certificate and has met the requirements of 14 CFR section
61.325; or
(d) The aircraft is operated by a student pilot:
(1) Who seeks a private pilot certificate and has met the requirements of 14 CFR section 61.95.
(2) Who seeks a recreational pilot or sport pilot certificate and has met the requirements of 14 CFR
section 61.94.
4. Unless otherwise authorized by ATC, each person operating a large turbine engine-powered airplane to
or from a primary airport must operate at or above the designated floors while within the lateral limits of Class
B airspace.
5. Unless otherwise authorized by ATC, each aircraft must be equipped as follows:
(a) For IFR operations, an operable VOR or TACAN receiver or an operable and suitable RNA V system;
and
(b) For all operations, a two-way radio capable of communications with ATC on appropriate frequencies
for that area; and
(c) Unless otherwise authorized by ATC, an operable radar beacon transponder with automatic altitude
reporting capability and operable ADS−B Out equipment.
NOTE−
ATC may, upon notification, immediately authorize a deviation from the altitude reporting equipment requirement; however,
a request for a deviation from the 4096 transponder equipment requirement must be submitted to the controlling ATC facility
at least one hour before the proposed operation. A request for a deviation from the ADS−B equipage requirement must be
submitted using the F AA’s automated web authorization tool at least one hour but not more than 24 hours before the proposed
operation.
REFERENCE−
AIM, Para 4−1−20, Transponder and ADS−B Out Operation.
AC 90−114, Automatic Dependent Surveillance−Broadcast Operations.
6. Mode C Veil. The airspace within 30 nautical miles of an airport listed in Appendix D, section 1 of 14
CFR part 91 (generally primary airports within Class B airspace areas), from the surface upward to 10,000 feet
MSL. Unless otherwise authorized by ATC, aircraft operating within this airspace must be equipped with an
operable radar beacon transponder with automatic altitude reporting capability and operable ADS −B Out
equipment.
However, aircraft that were not originally certificated with an engine−driven electrical system or that have not
subsequently been certified with a system installed may conduct operations within a Mode C veil provided the
aircraft remains outside Class A, B or C airspace; and below the altitude of the ceiling of a Class B or Class C
airspace area designated for an airport or 10,000 feet MSL, whichever is lower.
c. Charts. Class B airspace is charted on Sectional Charts, IFR En Route Low Altitude, and Terminal Area
Charts.
d. Flight Procedures.
1. Flights. Aircraft within Class B airspace are required to operate in accordan ce with current IFR
procedures. A clearance for a visual approach to a primary airport is not authorization for turbine − powered
airplanes to operate below the designated floors of the Class B airspace.
Controlled Airspace 3−2−3
AIM 2/20/25
2. VFR Flights.
(a) Arriving aircraft must obtain an ATC clearance prior to entering Class B airspace and must contact
ATC on the appropriate frequency, and in relation to geographical fixes shown on local charts. Although a pilot
may be operating beneath the floor of the Class B airspace on initial contact, communications with ATC should
be established in relation to the points indicated for spacing and sequencing purposes.
(b) Departing aircraft require a clearance to depart Class B airspace and should advise the clearance
delivery position of their intended altitude and route of flight. ATC will normally advise VFR aircraft when
leaving the geographical limits of the Class B airspace. Radar service is not automatically terminated with this
advisory unless specifically stated by the controller.
(c) Aircraft not landing or departing the primary airport may obtain an ATC clearance to transit the
Class B airspace when traffic conditions permit and provided the requirements of 14 CFR section 91.131 are met.
Such VFR aircraft are encouraged, to the extent possible, to operate at altitudes above or below the Class B
airspace or transit through established VFR corridors. Pilots operating in VFR corridors are urged to use
frequency 122.750 MHz for the exchange of aircraft position information.
e. ATC Clearances and Separation. An ATC clearance is required to enter and operate within Class B
airspace. VFR pilots are provided sequencing and separation from other aircraft while operating within Class
B airspace.
REFERENCE−
AIM, Para 4−1−18, Terminal Radar Services for VFR Aircraft.
NOTE−
Separation and sequencing of VFR aircraft will be suspended in the event of a radar outage as this service is dependent on
radar . The pilot will be advised that the service is not available and issued wind, runway information and the time or place
to contact the tower.
1. VFR aircraft are separated from all VFR/IFR aircraft which weigh 19,000 pounds or less by a minimum
of:
(a) Target resolution, or
(b) 500 feet vertical separation, or
(c) Visual separation.
2. VFR aircraft are separated from all VFR/IFR aircraft which weigh more than 19,000 and turbojets by
no less than:
(a) 1 1/2 miles lateral separation, or
(b) 500 feet vertical separation, or
(c) Visual separation.
3. This program is not to be interpreted as relieving pilots of their responsibilities to see and avoid other
traffic operating in basic VFR weather conditions, to adjust their operations and flight path as necessary to
preclude serious wake encounters, to maintain appropriate terrain and obstruction clearance or to remain in
weather conditions equal to or better than the minimums required by 14 CFR section 91.155. Approach control
should be advised and a revised clearance or instruction obtained when compliance with an assigned route,
heading and/or altitude is likely to compromise pilot responsibility with respect to terrain and obstruction
clearance, vortex exposure, and weather minimums.
4. ATC may assign altitudes to VFR aircraft that do not conform to 14 CFR section 91.159. “RESUME
APPROPRIATE VFR ALTITUDES” will be broadcast when the altitude assignment is no longer needed for
separation or when leaving Class B airspace. Pilots must return to an altitude that conforms to 14 CFR section
91.159.
f. Proximity Operations. VFR aircraft operating in proximity to Class B airspace are cautioned against
operating too closely to the boundaries, especially where the floor of the Class B airspace is 3,000 feet or less
3−2−4 Controlled Airspace
2/20/25 AIM
above the surface or where VFR cruise altitudes are at or near the floor of higher levels. Observance of this
precaution will reduce the potential for encountering an aircraft operating at the altitudes of Class B floors.
Additionally, VFR aircraft are encouraged to utilize the VFR Planning Chart as a tool for planning flight in
proximity to Class B airspace. Charted VFR Flyway Planning Charts are published on the back of the existing
VFR Terminal Area Charts.
3−2−4. Class C Airspace
a. Definition. Generally, that airspace from the surface to 4,000 feet above the airport elevation (charted in
MSL) surrounding those airports that have an operational control tower, are serviced by a radar approach control,
and that have a certain number of IFR operations or passenger enplanements. Although the configuration of each
Class C airspace area is individually tailored, the airspace usually consists of a 5 NM radius core surface area
that extends from the surface up to 4,000 feet above the airport elevation, and a 10 NM radius shelf area that
extends no lower than 1,200 feet up to 4,000 feet above the airport elevation.
b. Charts. Class C airspace is charted on Sectional Charts, IFR En Route Low Altitude, and Terminal Area
Charts where appropriate.
c. Operating Rules and Pilot/Equipment Requirements:
1. Pilot Certification. No specific certification required.
2. Equipment.
(a) Two-way radio; and
(b) Unless otherwise authorized by ATC, an operable radar beacon transponder with automatic altitude
reporting capability and operable ADS−B Out equipment.
NOTE−
See paragraph 4 −1−20, Transponder and ADS −B Out Operation, subparagraph f for Mode C transponder/ ADS −B
requirements for operating above Class C airspace.
3. Arrival or Through Flight Entry Requirements. Two-way radio communication must be established
with the ATC facility providing ATC services prior to entry and thereafter maintain those communications while
in Class C airspace. Pilots of arriving aircraft should contact the Class C airspace ATC facility on the publicized
frequency and give their position, altitude, radar beacon code, destination, and request Class C service. Radio
contact should be initiated far enough from the Class C airspace boundary to preclude entering Class C airspace
before two-way radio communications are established.
NOTE−
1. If the controller responds to a radio call with, “(aircraft callsign) standby,” radio communications have been established
and the pilot can enter the Class C airspace.
2. If workload or traffic conditions prevent immediate provision of Class C services, the controller will inform the pilot to
remain outside the Class C airspace until conditions permit the services to be provided.
3. It is important to understand that if the controller responds to the initial radio call without using the aircraft identification,
radio communications have not been established and the pilot may not enter the Class C airspace.
4. Class C airspace areas have a procedural Outer Area. Normally this area is 20 NM from the primary Class C airspace
airport. Its vertical limit extends from the lower limits of radio/radar coverage up to the ceiling of the approach control’ s
delegated airspace, excluding the Class C airspace itself, and other airspace as appropriate. (This outer area is not charted.)
5. Pilots approaching an airport with Class C service should be aware that if they descend below the base altitude of the
5 to 10 mile shelf during an instrument or visual approach, they may encounter non−transponder/non−ADS−B VFR aircraft.
EXAMPLE−
1. [Aircraft callsign] “remain outside the Class Charlie airspace and standby.”
2. “Aircraft calling Dulles approach control, standby.”
4. Departures from:
Controlled Airspace 3−2−5
AIM 2/20/25
(a) A primary or satellite airport with an operating control tower. Two-way radio communications must
be established and maintained with the control tower, and thereafter as instructed by ATC while operating in
Class C airspace.
(b) A satellite airport without an operating control tower. Two-way radio communications must be
established as soon as practicable after departing with the ATC facility having jurisdiction over the Class C
airspace.
5. Aircraft Speed. Unless otherwise authorized or required by ATC, no person may operate an aircraft at
or below 2,500 feet above the surface within 4 nautical miles of the primary airport of a Class C airspace area
at an indicated airspeed of more than 200 knots (230 mph).
d. Air Traffic Services. When two-way radio communications and radar contact are established, all VFR
aircraft are:
1. Sequenced to the primary airport.
2. Provided Class C services within the Class C airspace and the outer area.
3. Provided basic radar services beyond the outer area on a workload permitting basis. This can be
terminated by the controller if workload dictates.
e. Aircraft Separation. Separation is provided within the Class C airspace and the outer area after two-way
radio communications and radar contact are established. VFR aircraft are separated from IFR aircraft within the
Class C airspace by any of the following:
1. Visual separation.
2. 500 feet vertical separation.
3. Target resolution.
4. Wake turbulence separation will be provided to all aircraft operating:
(a) Behind and less than 1,000 feet below super or heavy aircraft,
(b) To small aircraft operating behind and less than 500 feet below B757 aircraft, and
(c) To small aircraft following a large aircraft on final approach.
NOTE−
1. Separation and sequencing of VFR aircraft will be suspended in the event of a radar outage as this service is dependent
on radar. The pilot will be advised that the service is not available and issued wind, runway information and the time or place
to contact the tower.
2. Pilot participation is voluntary within the outer area and can be discontinued, within the outer area, at the pilot’ s request.
Class C services will be provided in the outer area unless the pilot requests termination of the service.
3. Some facilities provide Class C services only during published hours. At other times, terminal IFR radar service will be
provided. It is important to note that the communications and transponder/ADS−B requirements are dependent on the class
of airspace established outside of the published hours.
f. Secondary Airports
1. In some locations Class C airspace may overlie the Class D surface area of a secondary airport. In order
to allow that control tower to provide service to aircraft, portions of the overlapping Class C airspace may be
procedurally excluded when the secondary airport tower is in operation. Aircraft operating in these procedurally
excluded areas will only be provided airport traffic control services when in communication with the secondary
airport tower.
2. Aircraft proceeding inbound to a satellite airport will be terminated at a sufficient distance to allow time
to change to the appropriate tower or advisory frequency. Class C services to these aircraft will be discontinued
when the aircraft is instructed to contact the tower or change to advisory frequency.
3−2−6 Controlled Airspace
AIM2/20/257/9/26 AIM
3. Aircraft departing secondary controlled airports will not receive Class C services until they have been
radar identified and two-way communications have been established with the Class C airspace facility.
4. This program is not to be interpreted as relieving pilots of their responsibilities to see and avoid other
traffic operating in basic VFR weather conditions, to adjust their operations and flight path as necessary to
preclude serious wake encounters, to maintain appropriate terrain and obstruction clearance or to remain in
weather conditions equal to or better than the minimums required by 14 CFR section 91.155. Approach control
should be advised and a revised clearance or instruction obtained when compliance with an assigned route,
heading and/or altitude is likely to compromise pilot responsibility with respect to terrain and obstruction
clearance, vortex exposure, and weather minimums.
g. Class C Airspace Areas by State. These states currently have designated Class C airspace areas that are
depicted on sectional charts. Pilots should consult current sectional charts and NOTAMs for the latest
information on services available. Pilots should be aware that some Class C airspace underlies or is adjacent to
Class B airspace. (See TBL 3−2−1.)
TBL 3−2−1
Class C Airspace Areas by State
State/City Airport
ALABAMA
Birmingham .........
Huntsville ...........
Mobile ..............
Birmingham−Shuttlesworth
International
International−Carl T Jones Fld
Regional
ALASKA
Anchorage ........... Ted Stevens International
ARIZONA
Davis−Monthan .......
Tucson ..............
AFB
International
ARKANSAS
Fayetteville (Springdale) Northwest Arkansas Regional
Little Rock .......... Adams Field
CALIFORNIA
Beale ...............
Burbank ............
Fresno ..............
Monterey ............
Oakland .............
Ontario .............
Riverside ............
Sacramento ..........
San Jose ............
Santa Ana ...........
Santa Barbara ........
AFB
Bob Hope
Yosemite International
Peninsula
Metropolitan Oakland
International
International
March AFB
International
Norman Y . Mineta International
John Wayne/Orange County
Municipal
COLORADO
Colorado Springs ..... Municipal
CONNECTICUT
Windsor Locks ....... Bradley International
FLORIDA
Daytona Beach .......
Fort Lauderdale .......
Fort Myers ..........
Jacksonville ..........
Orlando .............
International
Hollywood International
SW Florida Regional
International
Sanford International
State/City Airport
Palm Beach ..........
Pensacola ...........
Pensacola ...........
Sarasota .............
Tallahassee ..........
Whiting .............
President Donald J. Trump Inter-
national
NAS
International
Bradenton International
Regional
NAS
GEORGIA
Savannah ............ Hilton Head International
HAWAII
Kahului ............. Kahului
IDAHO
Boise ............... Air Terminal
ILLINOIS
Champaign .......... Urbana U of Illinois−Willard
Chicago .............
Moline ..............
Peoria ..............
Springfield ..........
Midway International
Quad City International
Greater Peoria Regional
Abraham Lincoln Capital
INDIANA
Evansville ...........
Fort Wayne ..........
Indianapolis ..........
South Bend ..........
Regional
International
International
Regional
IOWA
Cedar Rapids .........
Des Moines ..........
The Eastern Iowa
International
KANSAS
Wichita ............. Mid−Continent
KENTUCKY
Lexington ...........
Louisville ...........
Blue Grass
International−Standiford Field
LOUISIANA
Baton Rouge .........
Lafayette ............
Metropolitan, Ryan Field
Regional
Controlled Airspace 3−2−7
AIM 2/20/25
State/City Airport
Shreveport ........... Regional
MAINE
Bangor .............
Portland .............
International
International Jetport
MICHIGAN
Flint ................
Grand Rapids ........
Lansing .............
Bishop International
Gerald R. Ford International
Capital City
MISSISSIPPI
Columbus ...........
Jackson .............
AFB
Jackson−Evers International
MISSOURI
Springfield .......... Springfield−Branson National
MONTANA
Billings ............. Logan International
NEBRASKA
Lincoln .............
Omaha ..............
Offutt ...............
Lincoln
Eppley Airfield
AFB
NEV ADA
Reno ............... Reno/Tahoe International
NEW HAMPSHIRE
Manchester .......... Manchester
NEW JERSEY
Atlantic City ......... International
NEW MEXICO
Albuquerque ......... International Sunport
NEW YORK
Albany .............
Buffalo .............
Islip ................
Rochester ...........
Syracuse ............
International
Niagara International
Long Island MacArthur
Greater Rochester International
Hancock International
NORTH CAROLINA
Asheville ...........
Fayetteville ..........
Greensboro ..........
Pope ...............
Raleigh .............
Regional
Regional/Grannis Field
Piedmont Triad International
AFB
Raleigh−Durham International
OHIO
Akron ..............
Columbus ...........
Dayton .............
Toledo ..............
Akron−Canton Regional
Port Columbus International
James M. Cox International
Express
OKLAHOMA
Oklahoma City .......
Tinker ..............
Tulsa ...............
Will Rogers World
AFB
International
OREGON
Portland ............. International
State/City Airport
PENNSYLV ANIA
Allentown ........... Lehigh Valley International
PUERTO RICO
San Juan ............ Luis Munoz Marin International
RHODE ISLAND
Providence .......... Theodore Francis Green State
SOUTH CAROLINA
Charleston ...........
Columbia ............
Greer ...............
Myrtle Beach ........
Shaw ...............
AFB/International
Metropolitan
Greenville−Spartanburg
International
Myrtle Beach International
AFB
TENNESSEE
Chattanooga .........
Knoxville ...........
Nashville ............
Lovell Field
McGhee Tyson
International
TEXAS
Abilene .............
Amarillo ............
Austin ..............
Corpus Christi ........
Dyess ..............
El Paso .............
Harlingen ...........
Laughlin ............
Lubbock ............
Midland .............
San Antonio .........
Regional
Rick Husband International
Austin−Bergstrom International
International
AFB
International
Valley International
AFB
Preston Smith International
International
International
VERMONT
Burlington ........... International
VIRGIN ISLANDS
St. Thomas .......... Charlotte Amalie Cyril E. King
VIRGINIA
Richmond ...........
Norfolk .............
International
International
Roanoke ............ Regional/Woodrum Field
WASHINGTON
Point Roberts ........
Spokane ............
Spokane ............
Whidbey Island .......
Vancouver International
Fairchild AFB
International
NAS, Ault Field
WEST VIRGINIA
Charleston ........... Yeager
WISCONSIN
Green Bay ...........
Madison ............
Milwaukee ..........
Austin Straubel International
Dane County Regional−Traux
Field
General Mitchell International
3−2−5. Class D Airspace
a. Definition. Generally, Class D airspace extends upward from the surface to 2,500 feet above the airport
elevation (charted in MSL) surrounding those airports that have an operational control tower. The configuration
3−2−8 Controlled Airspace
2/20/25 AIM
of each Class D airspace area is individually tailored and when instrument procedures are published, the airspace
will normally be designed to contain the procedures.
1. Class D surface areas may be designated as full-time (24 hour tower operations) or part-time. Part-time
Class D effective times are published in the Chart Supplement.
2. Where a Class D surface area is part-time, the airspace may revert to either a Class E surface area (see
paragraph 3−2−6e1) or Class G airspace. When a part–time Class D surface area changes to Class G, the surface
area becomes Class G airspace up to, but not including, the overlying controlled airspace.
NOTE−
1. The airport listing in the Chart Supplement will state the part–time surface area status (for example, “other times CLASS
E” or “other times CLASS G”).
2. Normally, the overlying controlled airspace is the Class E transition area airspace that begins at either 700 feet AGL
(charted as magenta vignette) or 1200 feet AGL (charted as blue vignette). This may be determined by consulting the
applicable VFR Sectional or Terminal Area Charts.
b. Operating Rules and Pilot/Equipment Requirements:
1. Pilot Certification. No specific certification required.
2. Equipment. Unless otherwise authorized by ATC, an operable two−way radio is required.
3. Arrival or Through Flight Entry Requirements. Two−way radio communication must be established
with the ATC facility providing ATC services prior to entry and thereafter maintain those communications while
in the Class D airspace. Pilots of arriving aircraft should contact the control tower on the publicized frequency
and give their position, altitude, destination, and any request(s). Radio contact should be initiated far enough
from the Class D airspace boundary to preclude entering the Class D airspace before two −way radio
communications are established.
NOTE−
1. If the controller responds to a radio call with, “[aircraft callsign] standby,” radio communications have been established
and the pilot can enter the Class D airspace.
2. If workload or traffic conditions prevent immediate entry into Class D airspace, the controller will inform the pilot to
remain outside the Class D airspace until conditions permit entry.
EXAMPLE−
1. “[Aircraft callsign] remain outside the Class Delta airspace and standby.”
It is important to understand that if the controller responds to the initial radio call without using the aircraft callsign, radio
communications have not been established and the pilot may not enter the Class D airspace.
2. “Aircraft calling Manassas tower standby.”
At those airports where the control tower does not operate 24 hours a day, the operating hours of the tower will be listed
on the appropriate charts and in the Chart Supplement. During the hours the tower is not in operation, the Class E surface
area rules or a combination of Class E rules to 700 feet above ground level and Class G rules to the surface will become
applicable. Check the Chart Supplement for specifics.
4. Departures from:
(a) A primary or satellite airport with an operating control tower. Two-way radio communications must
be established and maintained with the control tower, and thereafter as instructed by ATC while operating in the
Class D airspace.
(b) A satellite airport without an operating control tower. Two-way radio communications must be
established as soon as practicable after departing with the ATC facility having jurisdiction over the Class D
airspace as soon as practicable after departing.
5. Aircraft Speed. Unless otherwise authorized or required by ATC, no person may operate an aircraft at
or below 2,500 feet above the surface within 4 nautical miles of the primary airport of a Class D airspace area
at an indicated airspeed of more than 200 knots (230 mph).
Controlled Airspace 3−2−9
AIM 2/20/253/15/077110.65R CHG 2AIM 8/7/25
c. Class D airspace areas are depicted on Sectional and Terminal charts with blue segmented lines, and on IFR
En Route Lows with a boxed [D].
d. Surface area arrival extensions:
1. Class D surface area arrival extensions for instrument approach procedures may be Class D or Class E
airspace. As a general rule, if all extensions are 2 miles or less, they remain part of the Class D surface area.
However, if any one extension is greater than 2 miles, then all extensions will be Class E airspace.
2. Surface area arrival extensions are effective during the published times of the surface area. For part–time
Class D surface areas that revert to Class E airspace, the arrival extensions will remain in effect as Class E
airspace. For part–time Class D surface areas that change to Class G airspace, the arrival extensions will become
Class G at the same time.
e. Separation for VFR Aircraft. No separation services are provided to VFR aircraft.
3−2−6. Class E Airspace
a. Definition. Class E airspace is controlled airspace that is designated to serve a variety of terminal or en
route purposes as described in this paragraph.
b. Operating Rules and Pilot/Equipment Requirements:
1. Pilot Certification. No specific certification required.
2. Equipment. Unless otherwise authorized by ATC:
(a) An operable radar beacon transponder with automatic altitude reporting capability and operable
ADS−B Out equipment are required at and above 10,000 feet MSL within the 48 contiguous states and the
District of Columbia, excluding the airspace at and below 2,500 feet above the surface, and
(b) Operable ADS−B Out equipment at and above 3,000 feet MSL over the Gulf of America from the
coastline of the United States out to 12 nautical miles.
NOTE−
The airspace described in (b) is specified in 14 CFR § 91.225 for ADS−B Out requirements. However, 14 CFR § 91.215 does
not include this airspace for transponder requirements.
3. Arrival or Through Flight Entry Requirements. No specific requirements.
c. Charts. Class E airspace below 14,500 feet MSL is charted on Sectional, Terminal, and IFR Enroute Low
Altitude charts.
d. Vertical limits. Except where designated at a lower altitude (see paragraph 3−2−6e, below, for specifics),
Class E airspace in the United States consists of:
1. The airspace extending upward from 14,500 feet MSL to, but not including, 18,000 feet MSL overlying
the 48 contiguous states, the District of Columbia and Alaska, including the waters within nautical 12 miles from
the coast of the 48 contiguous states and Alaska; excluding:
(a) The Alaska peninsula west of longitude 16000'00''W.; and
(b) The airspace below 1,500 feet above the surface of the earth unless specifically designated lower (for
example, in mountainous terrain higher than 13,000 feet MSL).
2. The airspace above FL 600 is Class E airspace.
e. Functions of Class E Airspace. Class E airspace may be designated for the following purposes:
1. Surface area designated for an airport where a control tower is not in operation. Class E surface
areas extend upward from the surface to a designated altitude, or to the adjacent or overlying controlled airspace.
The airspace will be configured to contain all instrument procedures.
(a) To qualify for a Class E surface area, the airport must have weather observation and reporting
capability, and communications capability must exist with aircraft down to the runway surface.
3−2−10 Controlled Airspace
2/20/25 AIM
(b) A Class E surface area may also be designated to accommodate part-time operations at a Class C or
Class D airspace location (for example, those periods when the control tower is not in operation).
(c) Pilots should refer to the airport page in the applicable Chart Supplement for surface area status
information.
2. Extension to a surface area. Class E airspace may be designated as extensions to Class B, Class C,
Class D, and Class E surface areas. Class E airspace extensions begin at the surface and extend up to the overlying
controlled airspace. The extensions provide contro lled airspace to contain st andard instrument approach
procedures without imposing a communications requirement on pilots operating under VFR. Surface area arrival
extensions become part of the surface area and are in effect during the same times as the surface area.
NOTE−
When a Class C or Class D surface area is not in effect continuously (for example, where a control tower only operates
part-time), the surface area airspace will change to either a Class E surface area or Class G airspace. In such cases, the
“Airspace” entry for the airport in the Chart Supplement will state “other times Class E” or “other times Class G.” When
a part-time surface area changes to Class E airspace, the Class E arrival extensions will remain in effect as Class E airspace.
If a part–time Class C, Class D, or Class E surface area becomes Class G airspace, the arrival extensions will change to
Class G at the same time.
3. Airspace used for transition. Class E airspace areas may be designated for transitioning aircraft
to/from the terminal or en route environment.
(a) Class E transition areas extend upward from either 700 feet AGL (shown as magenta vignette on
sectional charts) or 1,200 feet AGL (blue vignette) and are designated for airports with an approved instrument
procedure.
(b) The 700-foot/1200-foot AGL Class E airspace tr ansition areas remain in effect continuously,
regardless of airport operating hours or surface area status.
NOTE−
Do not confuse the 700-foot and 1200-foot Class E transition areas with surface areas or surface area extensions.
4. En Route Domestic Areas. There are Class E airspace areas that extend upward from a specified
altitude and are en route domestic airspace areas that provide controlled airspace in those areas where there is
a requirement to provide IFR en route ATC services but the Federal airway system is inadequate.
5. Federal Airways and Low-Altitude RNA V Routes. Federal airways and low-altitude RNA V routes are
Class E airspace areas and, unless otherwise specified, extend upward from 1,200 feet AGL to, but not
including,18,000 feet MSL.
(a) Federal airways consist of Low/Medium Frequency (L/MF) airways (colored Federal airways) and
VOR Federal airways.
(1) L/MF airways are based on non−directional beacons (NDB) and are identified as green, red, amber,
or blue.
(2) VOR Federal airways are based on VOR/VORTAC facilities and are identified by a “V” prefix.
(b) Low-altitude RNA V routes consist of T-routes and helicopter RNA V routes (TK-routes).
NOTE−
See AIM paragraph 5−3−4, Airways and Route Systems, for more details and charting information.
6. Offshore Airspace Areas. There are Class E airspace areas that extend upward from a specified altitude
to, but not including, 18,000 feet MSL and are designated as offshore airspace areas. These areas provide
controlled airspace beyond 12 miles from the coast of the U.S. in those areas where there is a requirement to
provide IFR en route ATC services and within which the U.S. is applying domestic procedures.
f. Separation for VFR Aircraft. No separation services are provided to VFR aircraft.
Controlled Airspace 3−2−11
2/20/25 AIM
Section 3. Class G Airspace
3−3−1. General
Class G airspace (uncontrolled) is that portion of airspace that has not been designated as Class A, Class B, Class
C, Class D, or Class E airspace.
3−3−2. VFR Requirements
Rules governing VFR flight have been adopted to assist the pilot in meeting the responsibility to see and avoid
other aircraft. Minimum flight visibility and distance from clouds required for VFR flight are contained in
14 CFR section 91.155. (See TBL 3−1−1.)
3−3−3. IFR Requirements
a. Title 14 CFR specifies the pilot and aircraft equipment requirements for IFR flight. Pilots are reminded that
in addition to altitude or flight level requirements, 14 CFR section 91.177 includes a requirement to remain at
least 1,000 feet (2,000 feet in designated mountainous terrain) above the highest obstacle within a horizontal
distance of 4 nautical miles from the course to be flown.
b. IFR Altitudes. (See TBL 3−3−1.)
TBL 3−3−1
IFR Altitudes
Class G Airspace
If your magnetic course
(ground track) is: And you are below 18,000 feet MSL, fly:
0 to 179 Odd thousands MSL, (3,000; 5,000; 7,000, etc.)
180 to 359 Even thousands MSL, (2,000; 4,000; 6,000, etc.)
Class G Airspace 3−3−1
2/20/25 AIM
Section 4. Special Use Airspace
3−4−1. General
a. Special use airspace (SUA) consists of that airspace wherein activities must be confined because of their
nature, or wherein limitations are imposed upon aircraft operations that are not a part of those activities, or both.
SUA areas are depicted on aeronautical charts, except for controlled firing areas (CFA), temporary military
operations areas (MOA), and temporary restricted areas.
b. Prohibited and restricted areas are regulatory special use airspace and are established in 14 CFR part 73
through the rulemaking process.
c. Warning areas, MOAs, alert areas, CFAs, and national security areas (NSA) are nonregulatory special use
airspace.
d. Special use airspace descriptions (except CFAs) are contained in FAA Order JO 7400.10, Special Use
Airspace.
e. Permanent SUA (except CFAs) is charted on Sectional Aeronautical, VFR Terminal Area, and applicable
En Route charts, and include the hours of operation, altitudes, and the controlling agency.
NOTE−
For temporary restricted areas and temporary MOAs, pilots should review the Domestic Notices found on the Federal
NOTAM System (FNS) NOTAM Search website under External Links or the Air Traffic Plans and Publications website, the
F AA SUA website, and/or contact the appropriate overlying ATC facility to determine the effect of non−depicted SUA areas
along their routes of flight.
3−4−2. Prohibited Areas
Prohibited areas contain airspace of defined dimensions identified by an area on the surface of the earth within
which the flight of aircraft is prohibited. Such areas are established for security or other reasons associated with
the national welfare. These areas are published in the Federal Register and are depicted on aeronautical charts.
3−4−3. Restricted Areas
a. Restricted areas contain airspace identified by an area on the surface of the earth within which the flight
of aircraft, while not wholly prohibited, is subject to restrictions. Activities within these areas must be confined
because of their nature or limitations imposed upon aircraft operations that are not a part of those activities or
both. Restricted areas denote the existence of unusual, often invisible, hazards to aircraft such as artillery firing,
aerial gunnery, or guided missiles. Penetration of restricted areas without authorization from the using or
controlling agency may be extremely hazardous to the aircraft and its occupants. Restricted areas are published
in the Federal Register and constitute 14 CFR part 73.
b. ATC facilities apply the following procedures when aircraft are operating on an IFR clearance (including
those cleared by ATC to maintain VFR-on-top) via a route which lies within joint-use restricted airspace.
1. If the restricted area is not active and has been released to the controlling agency (FAA), the ATC facility
will allow the aircraft to operate in the restricted airspace without issuing specific clearance for it to do so.
2. If the restricted area is active and has not been released to the controlling agency (FAA), the ATC facility
will issue a clearance which will ensure the aircraft avoids the restricted airspace unless it is on an approved
altitude reservation mission or has obtained its own permission to operate in the airspace and so informs the
controlling facility.
NOTE−
The above apply only to joint-use restricted airspace and not to prohibited and nonjoint-use airspace. For the latter
Special Use Airspace 3−4−1
AIM 2/20/25
categories, the ATC facility will issue a clearance so the aircraft will avoid the restricted airspace unless it is on an approved
altitude reservation mission or has obtained its own permission to operate in the airspace and so informs the controlling
facility.
c. Permanent restricted areas are charted on Sectional Aeronautical, VFR Terminal Area, and the appropriate
En Route charts.
NOTE−
Temporary restricted areas are not charted.
3−4−4. Warning Areas
A warning area is airspace of defined dimensions, extending from three nautical miles outward from the coast
of the U.S., that contains activity that may be hazardous to nonparticipating aircraft. The purpose of such warning
areas is to warn nonparticipating pilots of the potential danger. A warning area may be located over domestic
or international waters or both.
3−4−5. Military Operations Areas
a. MOAs consist of airspace of defined vertical and lateral limits established for the purpose of separating
certain military training activities from IFR traffic. Whenever a MOA is being used, nonparticipating IFR traffic
may be cleared through a MOA if IFR separation can be provided by ATC. Otherwise, ATC will reroute or restrict
nonparticipating IFR traffic.
b. Examples of activities conducted in MOAs include, but are not limited to: air combat tactics, air intercepts,
aerobatics, formation training, and low−altitude tactics. Military pilots flying in an active MOA are exempted
from the provisions of 14 CFR section 91.303(c) and (d) which prohibits aerobatic flight within Class D and Class
E surface areas, and within Federal airways. Additionally, the Department of Defense has been issued an
authorization to operate aircraft at indicated airspeeds in excess of 250 knots below 10,000 feet MSL within
active MOAs.
c. Pilots operating under VFR should exercise extreme caution while flying within a MOA when military
activity is being conducted. The activity status (active/inactive) of MOAs may change frequently. Therefore,
pilots should contact any FSS within 100 miles of the area to obtain accurate real-time information concerning
the MOA hours of operation. Prior to entering an active MOA, pilots should contact the controlling agency for
traffic advisories.
d. Permanent MOAs are charted on Sectional Aeronautical, VFR Terminal Area, and the appropriate En
Route Low Altitude charts.
NOTE−
Temporary MOAs are not charted.
3−4−6. Alert Areas
Alert areas are depicted on aeronautical charts to inform nonparticipating pilots of areas that may contain a high
volume of pilot training or an unusual type of aerial activity. Pilots should be particularly alert when flying in
these areas. All activity within an alert area must be conducted in accordance with CFRs, without waiver, and
pilots of participating aircraft as well as pilots transiting the area must be equally responsible for collision
avoidance.
3−4−7. Controlled Firing Areas
CFAs contain activities which, if not conducted in a controlled environment, could be hazardous to
nonparticipating aircraft. The distinguishing feature of the CFA, as compared to other special use airspace, is that
its activities are suspended immediately when spotter aircraft, radar, or ground lookout positions indicate an
aircraft might be approaching the area. There is no need to chart CFAs since they do not cause a nonparticipating
aircraft to change its flight path.
3−4−2 Special Use Airspace
2/20/25 AIM
3−4−8. National Security Areas
NSAs consist of airspace of defined vertical and lateral dimensions established at locations where there is a
requirement for increased security and safety of ground facilities. Pilots are requested to voluntarily avoid flying
through the depicted NSA. When it is necessary to provide a greater level of security and safety, flight in NSAs
may be temporarily prohibited by regulation under the provisions of 14 CFR section 99.7. Regulatory
prohibitions will be issued by System Operations Security and disseminated via NOTAM. Inquiries about NSAs
should be directed to System Operations Security.
REFERENCE−
AIM, Para 5−6−1, National Security
3−4−9. Obtaining Special Use Airspace Status
a. Pilots can request the status of SUA by contacting the using or controlling agency. The frequency for the
controlling agency is tabulated in the margins of the applicable IFR and VFR charts.
b. An airspace NOTAM will be issued for SUA when the SUA airspace (permanent and/or temporary)
requires a NOTAM for activation. Pilots should check ARTCC NOTAMs for airspace activation.
c. Special Use Airspace Information Service (SUAIS) (Alaska Only). The SUAIS is a 24−hour service
operated by the military that provides civilian pilots, flying VFR, with information regarding military flight
operations in certain MOAs and restricted airspace within central Alaska. The service provides “near real time”
information on military flight activity in the interior Alaska MOA and Restricted Area complex. SUAIS also
provides information on artillery firing, known helicopter operations, and unmanned aerial vehicle operations.
Pilots flying VFR are encouraged to use SUAIS. See the Alaska Chart Supplement for hours of operation, phone
numbers, and radio frequencies.
d. Special use airspace scheduling data for preflight planning is available via the FAA SUA website.
Special Use Airspace 3−4−3
2/20/25 AIM
Section 5. Other Airspace Areas
3−5−1. Airport Advisory/Information Services
a. There are two advisory type services available at selected airports.
1. Local Airport Advisory (LAA) service is available only in Alaska and is operated within 10 statute miles
of an airport where a control tower is not operating but where a FSS is located on the airport. At such locations,
the FSS provides a complete local airport advisory service to arriving and departing aircraft. During periods of
fast changing weather the FSS will automatically provide Final Guard as part of the service from the time the
aircraft reports “on −final” or “taking −the−active−runway” until the aircraft reports “on −the−ground” or
“airborne.”
NOTE−
Current policy, when requesting remote ATC services, requires that a pilot monitor the automated weather broadcast at the
landing airport prior to requesting ATC services. The FSS automatically provides Final Guard, when appropriate, during
LAA/Remote Airport Advisory (RAA) operations. Final Guard is a value added wind/altimeter monitoring service, which
provides an automatic wind and altimeter check during active weather situations when the pilot reports on−final or taking
the active runway. During the landing or take−off operation when the winds or altimeter are actively changing the FSS will
blind broadcast significant changes when the specialist believes the change might affect the operation. Pilots should
acknowledge the first wind/altimeter check but due to cockpit activity no acknowledgement is expected for the blind
broadcasts. It is prudent for a pilot to report on−the−ground or airborne to end the service.
2. Remote Airport Information Service (RAIS) is provided in support of short term special events like small
to medium fly−ins. The service is advertised by NOTAM D only. The FSS will not have access to a continuous
readout of the current winds and altimeter; therefore, RAIS does not include weather and/or Final Guard service.
However, known traffic, special event instructions, and all other services are provided.
NOTE−
The airport authority and/or manager should request RAIS support on official letterhead directly with the manager of the
FSS that will provide the service at least 30 days in advance. Approval authority rests with the FSS manager and is based
on workload and resource availability.
REFERENCE−
AIM, Para 4−1−9, Traffic Advisory Practices at Airports Without Operating Control Towers.
b. It is not mandatory that pilots participate in the Airport Advisory programs. Participation enhances safety
for everyone operating around busy GA airports; therefore, everyone is encouraged to participate and provide
feedback that will help improve the program.
3−5−2. Military Training Routes
a. National security depends largely on the deterrent effect of our airborne military forces. To be proficient,
the military services must train in a wide range of airborne tactics. One phase of this training involves “low level”
combat tactics. The required maneuvers and high sp eeds are such that they may occasionally make the
see-and-avoid aspect of VFR flight more difficult without increased vigilance in areas containing such
operations. In an effort to ensure the greatest practical level of safety for all flight operations, the Military
Training Route (MTR) program was conceived.
b. The MTR program is a joint venture by the FAA and the Department of Defense (DoD). MTRs are mutually
developed for use by the military for the purpose of conducting low-altitude, high-speed training. The routes
above 1,500 feet AGL are developed to be flown, to the maximum extent possible, under IFR. The routes at 1,500
feet AGL and below are generally developed to be flown under VFR.
c. Generally, MTRs are established below 10,000 feet MSL for operations at speeds in excess of 250 knots.
However, route segments may be defined at higher altitudes for purposes of route continuity. For example, route
segments may be defined for descent, climbout, and mountainous terrain. There are IFR and VFR routes as
follows:
Other Airspace Areas 3−5−1
AIM 2/20/25
1. IFR Military Training Routes−(IR). Operations on these routes are conducted in accordance with IFR
regardless of weather conditions.
2. VFR Military Training Routes−(VR). Operations on these routes are conducted in accordance with
VFR except flight visibility must be 5 miles or more; and flights must not be conducted below a ceiling of less
than 3,000 feet AGL.
d. Military training routes will be identified and charted as follows:
1. Route identification.
(a) MTRs with no segment above 1,500 feet AGL must be identified by four number characters; e.g.,
IR1206, VR1207.
(b) MTRs that include one or more segments above 1,500 feet AGL must be identified by three number
characters; e.g., IR206, VR207.
(c) Alternate IR/VR routes or route segments are identified by using the basic/principal route designation
followed by a letter suffix, e.g., IR008A, VR1007B, etc.
2. Route charting.
(a) IFR Enroute Low Altitude Chart. This chart will depict all IR routes and all VR routes that
accommodate operations above 1,500 feet AGL.
(b) VFR Sectional Aeronautical Charts. These charts will depict military training activities such as IR
and VR information. Special Military Activity Routes (SMARs) may also be charted on the VFR Sectional Chart,
showing the extent of the airspace allocated to the associated IFR Military Training Routes within which the
Department of Defense conducts periodic operations involving Unmanned Aircraft Systems. These aircraft may
be accompanied by military or other aircraft that provide the pilots of the Unmanned Aircraft Systems visual
observation information about other aircraft operations near them. Further information on SMAR charting can
be found on the border of the printed VFR Sectional Chart and in the FAA Aeronautical Chart Users’ Guide
available online at: https://www.faa.gov/air_traffic/flight_info/aeronav/digital_products/aero_guide/.
(c) Area Planning (AP/1B) Chart (DoD Flight Information Publication −FLIP). This chart is
published by the National Geospatial −Intelligence Agency (NGA) primarily for military users and contains
detailed information on both IR and VR routes.
REFERENCE−
AIM, Para 9−1−6, Subpara a, National Geospatial−Intelligence Agency (NGA) Products.
e. DoD FLIP− Department of Defense Flight Information Publications describe IR/VR routes through charts
and narratives, and the FAA provides information regarding these routes to all users via IFR and VFR charts.
NOTE−
DoD users that require copies of FLIP should contact:
Defense Logistics Agency for Aviation
Mapping Customer Operations (DLA AVN/QAM)
8000 Jefferson Davis Highway
Richmond, VA 23297−5339
Toll free phone: 1−800−826−0342
Commercial: 804−279−6500
MTR information from the FLIP is available for pilot briefings through Flight Service. (See subparagraph f
below.)
f. Availability of MTR information.
1. Pilots may obtain preflight MTR information through Flight Service (see paragraph 5 −1−1, Preflight
Preparation).
2. MTR routes are depicted on IFR En Route Low Altitude Charts and VFR Sectional Charts, which are
available for free download on the FAA website at
https://www.faa.gov/air_traffic/flight_info/aeronav/digital_products/.
3−5−2 Other Airspace Areas
2/20/25 AIM
g. Nonparticipating aircraft are not prohibited from flying within an MTR or SMAR; however, extreme
vigilance should be exercised when conducting flight through or near these routes. Pilots, while inflight, should
contact the FSS within 100 NM of a particular MTR to obtain current information or route usage in their vicinity.
Information available includes times of scheduled activity, altitudes in use on each route segment, and actual
route width. Route width varies for each MTR and can extend several miles on either side of the charted MTR
centerline. Route width information for IFR Military Training Route (IR) and VFR Military Training Route (VR)
MTRs is also available in the FLIP AP/1B along with additional MTR (slow routes/air refueling routes)
information. When requesting MTR information, pilots should give the FSS the MTR designation of interest,
their position, route of flight, and destination in order to reduce frequency congestion and permit the FSS
specialist to identify the MTR or SMAR that could be a factor.
3−5−3. Temporary Flight Restrictions
a. General. This paragraph describes the types of conditions under which the FAA may impose temporary
flight restrictions. It also explains which FAA elements have been delegated authority to issue a temporary flight
restrictions NOTAM and lists the types of responsible agencies/offices from which the FAA will accept requests
to establish temporary flight restrictions. The 14 CFR is explicit as to what operations are prohibited, restricted,
or allowed in a temporary flight restrictions area. Pilots are responsible to comply with 14 CFR sections 91.137,
91.138, 91.141 and 91.143 when conducting flight in an area where a temporary flight restrictions area is in
effect, and should check appropriate NOTAMs during flight planning.
b. The purpose for establishing a temporary flight restrictions area is to:
1. Protect persons and property in the air or on the surface from an existing or imminent hazard associated
with an incident on the surface when the presence of low flying aircraft would magnify, alter, spread, or
compound that hazard (14 CFR section 91.137(a)(1));
2. Provide a safe environment for the operation of disaster relief aircraft (14 CFR section 91.137(a)(2)); or
3. Prevent an unsafe congestion of sightseeing aircraft above an incident or event which may generate a high
degree of public interest (14 CFR section 91.137(a)(3)).
4. Protect declared national disasters for humanita rian reasons in the State of Hawaii (14 CFR
section 91.138).
5. Protect the President, Vice President, or other public figures (14 CFR section 91.141).
6. Provide a safe environment for space agency operations (14 CFR section 91.143).
c. Except for hijacking situations, when the provisions of 14 CFR section 91.137(a)(1) or (a)(2) are necessary,
a temporary flight restrictions area will only be established by or through the area manager at the Air Route
Traffic Control Center (ARTCC) having jurisdiction over the area concerned. A temporary flight restrictions
NOTAM involving the conditions of 14 CFR section 91.137(a)(3) will be issued at the direction of the service
area office director having oversight of the airspace concerned. When hijacking situations are involved, a
temporary flight restrictions area will be implemented through the TSA Aviation Command Center. The
appropriate FAA air traffic element, upon receipt of such a request, will establish a temporary flight restrictions
area under 14 CFR section 91.137(a)(1).
d. The FAA accepts recommendations for the establishment of a temporary flight restrictions area under
14 CFR section 91.137(a)(1) from military major command headquarters, regional directors of the Office of
Emergency Planning, Civil Defense State Directors, State Governors, or other similar authority. For the
situations involving 14 CFR section 91.137(a)(2), the FAA accepts recommendations from military commanders
serving as regional, subregional, or Search and Rescue (SAR) coordinators; by military commanders directing
or coordinating air operations associated with disaster relief; or by civil authorities directing or coordinating
organized relief air operations (includes representatives of the Office of Emergency Planning, U.S. Forest
Service, and State aeronautical agencies). Appropria te authorities for a temporary flight restrictions
establishment under 14 CFR section 91.137(a)(3) are any of those listed above or by State, county, or city
government entities.
Other Airspace Areas 3−5−3
AIM 2/20/25
e. The type of restrictions issued will be kept to a minimum by the FAA consistent with achievement of the
necessary objective. Situations which warrant the extreme restrictions of 14 CFR section 91.137(a)(1) include,
but are not limited to: toxic gas leaks or spills, flammable agents, or fumes which if fanned by rotor or propeller
wash could endanger persons or property on the surface, or if entered by an aircraft could endanger persons or
property in the air; imminent volcano eruptions which could endanger airborne aircraft and occupants; nuclear
accident or incident; and hijackings. Situations which warrant the restrictions associated with 14 CFR
section 91.137(a)(2) include: forest fires which are being fought by releasing fire retardants from aircraft; and
aircraft relief activities following a disaster (earthquake, tidal wave, flood, etc.). 14 CFR section 91.137(a)(3)
restrictions are established for events and incidents that would attract an unsafe congestion of sightseeing aircraft.
f. The amount of airspace needed to protect persons and property or provide a safe environment for
rescue/relief aircraft operations is normally limited to within 2,000 feet above the surface and within a
3−nautical−mile radius. Incidents occurring within Class B, Class C, or Class D airspace will normally be
handled through existing procedures and should not require the issuance of a temporary flight restrictions
NOTAM. Temporary flight restrictions affecting airspace outside of the U.S. and its territories and possessions
are issued with verbiage excluding that airspace outside of the 12−mile coastal limits.
g. The FSS nearest the incident site is normally the “coordination facility.” When FAA communications
assistance is required, the designated FSS will function as the primary communications facility for coordination
between emergency control authorities and affected aircraft. The ARTCC may act as liaison for the emergency
control authorities if adequate communications cannot be established between the designated FSS and the relief
organization. For example, the coordination facility may relay authorizations from the on-scene emergency
response official in cases where news media aircraft operations are approved at the altitudes used by relief
aircraft.
h. ATC may authorize operations in a temporary flight restrictions area under its own authority only when
flight restrictions are established under 14 CFR section 91.137(a)(2) and (a)(3). The appropriate ARTCC/airport
traffic control tower manager will, however, ensure that such authorized flights do not hamper activities or
interfere with the event for which restrictions were implemented. However, ATC will not authorize local IFR
flights into the temporary flight restrictions area.
i. To preclude misunderstanding, the implementing NOTAM will contain specific and formatted information.
The facility establishing a temporary flight restrictions area will format a NOTAM beginning with the phrase
“FLIGHT RESTRICTIONS” followed by: the location of the temporary flight restrictions area; the effective
period; the area defined in statute miles; the altitudes affected; the FAA coordination facility and commercial
telephone number; the reason for the temporary flight restrictions; the agency directing any relief activities and
its commercial telephone number; and other information considered appropriate by the issuing authority.
EXAMPLE−
1. 14 CFR section 91.137(a)(1):
The following NOTAM prohibits all aircraft operations except those specified in the NOTAM.
Flight restrictions Matthews, Virginia, effective immediately until 9610211200. Pursuant to 14 CFR section 91.137(a)(1)
temporary flight restrictions are in effect. Rescue operations in progress. Only relief aircraft operations under the direction
of the Department of Defense are authorized in the airspace at and below 5,000 feet MSL within a 2−nautical−mile radius
of Laser AFB, Matthews, Virginia. Commander, Laser AFB, in charge (897) 946 −5543 (122.4). Steenson FSS
(792) 555−6141 (123.1) is the F AA coordination facility.
2. 14 CFR section 91.137(a)(2):
The following NOTAM permits flight operations in accordance with 14 CFR section 91.137(a)(2). The on-site emergency
response official to authorize media aircraft operations below the altitudes used by the relief aircraft. Flight restrictions 25
miles east of Bransome, Idaho, effective immediately until 9601202359 UTC. Pursuant to 14 CFR section 91.137(a)(2)
temporary flight restrictions are in effect within a 4−nautical−mile radius of the intersection of county roads 564 and 315
at and below 3,500 feet MSL to provide a safe environment for fire fighting aircraft operations. Davis County sheriff’ s
department (792) 555−8122 (122.9) is in charge of on-scene emergency response activities. Glivings FSS (792) 555−1618
(122.2) is the F AA coordination facility.
3−5−4 Other Airspace Areas
2/20/25 AIM
3. 14 CFR section 91.137(a)(3):
The following NOTAM prohibits sightseeing aircraft operations.
Flight restrictions Brown, Tennessee, due to olympic activity. Effective 9606181100 UTC until 9607190200 UTC. Pursuant
to 14 CFR section 91.137(a)(3) temporary fli ght restrictions are in effect within a 3 −nautical− mile radius of
N355783/W835242 and Volunteer VORTAC 019 degree radial 3.7 DME fix at and below 2,500 feet MSL. Norton FSS (423)
555−6742 (126.6) is the F AA coordination facility.
4. 14 CFR section 91.138:
The following NOTAM prohibits all aircraft except those operating under the authorization of the official in charge of
associated emergency or disaster relief response activities, aircraft carrying law enforcement officials, aircraft carrying
personnel involved in an emergency or legitimate scientific purposes, carrying properly accredited news media, and aircraft
operating in accordance with an ATC clearance or instruction.
Flight restrictions Kapalua, Hawaii, effective 9605101200 UTC until 9605151500 UTC. Pursuant to 14 CFR
section 91.138 temporary flight restrictions are in effect within a 3 −nautical−mile radius of N205778/W1564038 and
Maui/OGG/VORTAC 275 degree radial at 14.1 nautical miles. John Doe 808 −757−4469 or 122.4 is in charge of the
operation. Honolulu/HNL 808−757−4470 (123.6) FSS is the FAA coordination facility.
5. 14 CFR section 91.141:
The following NOTAM prohibits all aircraft.
Flight restrictions Stillwater, Oklahoma, June 21, 1996. Pursuant to 14 CFR section 91.141 aircraft flight operations are
prohibited within a 3−nautical−mile radius, below 2000 feet AGL of N360962/W970515 and the Stillwater/SWO/VOR/DME
176 degree radial 3.8−nautical−mile fix from 1400 local time to 1700 local time June 21, 1996, unless otherwise authorized
by ATC.
6. 14 CFR section 91.143:
The following NOTAM prohibits any aircraft of U.S. registry, or pilot any aircraft under the authority of an airman certificate
issued by the F AA.
Kennedy space center space operations area effective immediately until 9610152100 UTC. Pursuant to 14 CFR section
91.143, flight operations conducted by F AA certificated pilots or conducted in aircraft of U.S. registry are prohibited at any
altitude from surface to unlimited, within the following area 30−nautical−mile radius of the Melbourne/MLB/VORTAC 010
degree radial 21−nautical−mile fix. St. Petersburg, Florida/PIE/FSS 813−545−1645 (122.2) is the F AA coordination facility
and should be contacted for the current status of any airspace associated with the space shuttle operations. This airspace
encompasses R2933, R2932, R2931, R2934, R2935, W497A and W158A. Additional warning and restricted areas will be
active in conjunction with the operations. Pilots must consult all NOTAMs regarding this operation.
3−5−4. Parachute Jump Aircraft Operations
a. Procedures relating to parachute jump areas are contained in 14 CFR part 105. Tabulations of parachute
jump areas in the U.S. are contained in the Chart Supplement.
b. Pilots of aircraft engaged in parachute jump operations are reminded that all reported altitudes must be with
reference to mean sea level, or flight level, as a ppropriate, to enable ATC to provide meaningful traffic
information.
c. Parachute operations in the vicinity of an airport without an operating control tower − there is no substitute
for alertness while in the vicinity of an airport. It is essential that pilots conducting parachute operations be alert,
look for other traffic, and exchange traffic information as recommended in paragraph 4−1−9, Traffic Advisory
Practices at Airports Without Operating Control Towers. In addition, pilots should avoid releasing parachutes
while in an airport traffic pattern when there are other aircraft in that pattern. Pilots should make appropriate
broadcasts on the designated Common Traffic Advisory Frequency (CTAF), and monitor that CTAF until all
parachute activity has terminated or the aircraft has left the area. Prior to commencing a jump operation, the pilot
should broadcast the aircraft’s altitude and position in relation to the airport, the approximate relative time when
the jump will commence and terminate, and listen to the position reports of other aircraft in the area.
3−5−5. Published VFR Routes
Published VFR routes for transitioning around, under and through complex airspace such as Class B airspace
were developed through a number of FAA and industry initiatives. All of the following terms, i.e., “VFR Flyway”
Other Airspace Areas 3−5−5
AIM 2/20/25
“VFR Corridor” and “VFR Transition Route” have been used when referring to the same or different types of
routes or airspace. The following paragraphs identify and clarify the functionality of each type of route and
specify where and when an ATC clearance is required.
a. VFR Flyways.
1. A VFR Flyway is defined as a general flight path not defined as a specific course, for use by pilots in
planning flights into, out of, through or near complex terminal airspace to avoid Class B airspace. An ATC
clearance is NOT required to fly these routes.
FIG 3−5−1
VFR Flyway Planning Chart
2. VFR Flyways are depicted on the reverse side of some VFR Terminal Area Charts (TACs ). (See FIG
3−5−1.) These charts identify VFR Flyways designed to help VFR pilots avoid major controlled traffic flows.
They may further depict multiple VFR routings throughout the area which may be used as an alternative to flight
within Class B airspace. The ground references provide a guide for improved visual navigation. These routes are
not intended to discourage requests for VFR operations within Class B airspace but are designed solely to assist
pilots in planning for flights under and around busy Class B airspace without entering ClassB airspace.
3. It is very important to remember that these suggested routes are not sterile of other traffic. The entire
Class B airspace, and the airspace underneath it, may be heavily congested with many different types of aircraft.
3−5−6 Other Airspace Areas
AIM2/20/258/7/25 AIM
Pilot adherence to VFR rules must be exercised at all times. Communications must be established and maintained
between your aircraft and any control tower while transiting Class–C or Class D surface areas of airports under
Class B airspace.
b. VFR Corridors.
1. The design of a few of the first Class B airspace areas provided a corridor for the passage of uncontrolled
traffic. A VFR corridor is defined as airspace through Class B airspace, with defined vertical and lateral
boundaries, in which aircraft may operate without an ATC clearance or communication with air traffic control.
2. These corridors are, in effect, a “hole” through Class B airspace. (See FIG 3−5−2.) A classic example
would be the corridor through the Los Angeles Class B airspace, which has been subsequently changed to Special
Flight Rules airspace (SFR). A corridor is surrounded on all sides by Class B airspace and does not extend down
to the surface like a VFR Flyway. Because of their finite lateral and vertical limits, and the volume of VFR traffic
using a corridor, extreme caution and vigilance must be exercised.
FIG 3−5−2
Class B Airspace
3. Because of the heavy traffic volume and the procedures necessary to efficiently manage the flow of
traffic, it has not been possible to incorporate VFR corridors in the development or modifications of Class B
airspace in recent years.
c. VFR Transition Routes.
1. To accommodate VFR traffic through terminal airspace, VFR Transition Routes were developed. A VFR
Transition Route is defined as a specific flight course depicted and described on a TAC and/or VFR Flyway
Planning Chart. Communication with ATC where the route transitions Class B, Class C, and/or Class D airspace
is required. In addition to communication requirements, a clearance is required to operate in Class B airspace.
VFR Transition Routes may include published altitudes or ATC-assigned altitudes. Per 14 CFR section 91.123,
pilot compliance is expected for all route and altitude restrictions as published or assigned by ATC. VFR
Transition Route and altitude assignments do not relieve pilots from their duty to comply with 14 CFR section
91.119. Pilots are expected to request an alternate clearance if necessary for compliance.
2. These routes, as depicted in FIG 3− 5−3, are designed to show the pilot where to position the aircraft
where an ATC assignment or clearance for the route can normally be expected with minimal or no delay. Until
ATC authorization is received, pilots must remain clear of Class B airspace. On initial contact, pilots should
advise ATC of their position, altitude, route name desired, and direction of flight.
3. For secondary airports underlying or in close proximity to Class B or Class C airspace, VFR Transition
Routes may be developed and depicted for arrivals/departures. These arrivals/departures may be requested from
or assigned by ATC.
Other Airspace Areas 3−5−7
AIM 2/20/253/15/077110.65R CHG 2AIM 1/22/26
FIG 3−5−3
VFR Transition Route
d. Helicopter Route Chart.
1. Helicopter Routes are depicted on a specialized VFR chart established for select high traffic density areas
to enhance helicopter access and ease of operation. The Helicopter Route Chart depicts prominent geographical
features, roads and obstructions. A Helicopter Route is a specific VFR flight course and is depicted on the
Helicopter Route Chart. These routes contain specific altitudes and instructions for navigating over visual
reference points as published, or as instructed by ATC.
2. Helicopter Route Charts, as depicted in FIG 3−5−4, incorporate expanded ground reference and unique
symbology to improve visual navigation. The charts contain additional information such as frequencies to
self−announce on and other route information. On initial contact, pilots should advise ATC of their position,
altitude, and route name desired. Helicopter Routes may include published altitudes or ATC-assigned altitudes.
Per 14 CFR section 91.123, pilot compliance is expected for all route and altitude restrictions as published or
assigned by ATC. Helicopter Route and altitude assignments do not relieve pilots from their duty to comply with
14 CFR section 91.119 and 132.203(b). Pilots are expected to request an alternate clearance if necessary for
compliance.
3. VFR Helicopter routes are available at the following website:
https://www.faa.gov/air_traffic/flight_info/aeronav/digital_products/vfr/.
3−5−8 Other Airspace Areas
AIM2/20/258/7/25 AIM
FIG 3−5−4
Helicopter Route Chart
3−5−6. Terminal Radar Service Area (TRSA)
a. Background. TRSAs were originally established as part of the Terminal Radar Program at selected
airports. TRSAs were never controlled airspace from a regulatory standpoint because the establishment of
TRSAs was never subject to the rulemaking process; consequently, TRSAs are not contained in 14 CFR part 71
nor are there any TRSA operating rules in 14 CFR part 91. Part of the Airport Radar Service Area (ARSA)
program was to eventually replace all TRSAs. However, the ARSA requirements became relatively stringent and
it was subsequently decided that TRSAs would have to meet ARSA criteria before they would be converted.
TRSAs do not fit into any of the U.S. airspace classes; therefore, they will continue to be non−part 71 airspace
areas where participating pilots can receive additional radar services which have been redefined as TRSA
Service.
b. TRSAs. The primary airport(s) within the TRSA become(s) Class D airspace. The remaining portion of
the TRSA overlies other controlled airspace which is normally Class E airspace beginning at 700 or 1,200 feet
and established to transition to/from the en route/terminal environment.
c. Participation. Pilots operating under VFR are encouraged to contact the radar approach control and avail
themselves of the TRSA Services. However, participation is voluntary on the part of the pilot. See Chapter 4,
Air Traffic Control, for details and procedures.
d. Charts. TRSAs are depicted on VFR sectional and terminal area charts with a solid black line and altitudes
for each segment. The Class D portion is charted with a blue segmented line.
Other Airspace Areas 3−5−9
AIM 2/20/25
3−5−7. Special Air Traffic Rules (SATR) and Special Flight Rules Area (SFRA)
a. Background. The Code of Federal Regulations (CFR) prescribes special air traffic rules for aircraft
operating within the boundaries of certain designated airspace. These areas are listed in 14 CFR part 93 and can
be found throughout the NAS. Procedures, nature of operations, configuration, size, and density of traffic vary
among the identified areas.
b. SFRAs. Airspace of defined dimensions, above land areas or territorial waters, within which the flight of
aircraft is subject to the rules set forth in 14 CFR part 93, unless otherwise authorized by air traffic control. Not
all areas listed in 14 CFR part 93 are designated SFRA, but special air traffic rules apply to all areas described
in 14 CFR part 93.
REFERENCE−
14 CFR Part 93, Special Air Traffic Rules
F AA Order JO 7110.65, Para 9−2−10, Special Air Traffic Rules (SATR) and Special Flight Rules Area (SFRA)
P/CG − Special Air Traffic Rules (SATR)
c. Participation. Each person operating an aircraft to, from, or within airspace designated as a SATR area or
SFRA must adhere to the special air traffic rules set forth in 14 CFR part 93, as applicable, unless otherwise
authorized or required by ATC.
d. Charts. SFRAs are depicted on VFR sectional, terminal area, and helicopter route charts. (See FIG 3−5−5.)
FIG 3−5−5
SFRA Boundary
e. Additional information and resources regarding SFRA, including procedures for flight in individual areas,
may be found on the FAA Safety website at http://www.faasafety.gov
3−5−8. Washington, DC, Special Flight Rules Area (SFRA) including the Flight Restricted
Zone (FRZ)
A pilot conducting any type of flight operation in the Washington, DC, SFRA/FRZ must comply with the
requirements in:
a. 14 CFR section 93.339, Washington, DC, Metropolitan Area Special Flight Rules Area including the FRZ.
b. 14 CFR section 91.161, Special Awareness Training for the DC SFRA/FRZ, also located on the FAA
website at https://www.faasafety.gov/.
c. Any 14 CFR section 99.7 special security instructions for the DC SFRA/FRZ published via NOTAM by
FAA in the interest of national security.
3−5−9. Weather Reconnaissance Area (WRA)
a. General. Hurricane Hunters from the United States Air Force Reserve 53 rd Weather Reconnaissance
Squadron (WRS) and the National Oceanic and Atmospheric Administration (NOAA) Aircraft Operations
3−5−10 Other Airspace Areas
AIM2/20/258/7/25 AIM
Center (AOC) operate weather reconnaissance/research aircraft missions, in support of the National Hurricane
Operations Plan (NHOP), to gather meteorological data on hurricanes and tropical cyclones. 53 rd WRS and
NOAA AOC aircraft normally conduct these missions in airspace identified in a published WRA Notice to
Airmen (NOTAM).
b. WRAs. Airspace with defined dimensions and published by a NOTAM, which is established to support
weather reconnaissance/research flights. ATC services are not provided within WRAs. Only participating
weather reconnaissance/research aircraft from the 53rd WRS and NOAA AOC are permitted to operate within
a WRA. A WRA may only be established in airspace within U. S. Flight Information Regions (FIR) outside of
U. S. territorial airspace.
c. A published WRA NOTAM describes the airspace dimensions of the WRA and the expected activities
within the WRA. WRAs may border adjacent foreign FIRs, but are wholly contained within U.S. FIRs. As ATC
services are not provided within a WRA, non−participating aircraft should avoid WRAs, and IFR aircraft should
expect to be rerouted to avoid WRAs.
3−5−10. Other Non− Charted Airspace Areas
a. Stationary or Moving Altitude Reservation (ALTRV). A Stationary or Moving ALTRV is announced via
an airspace NOTAM issued by the Central Altitude Reservation Facility (CARF) or ARTCC. These
announcements will appear in CARF and/or ARTCC NOTAMS. This airspace ensures non−participating IFR
aircraft remain separated from special activity. Non−participating VFR aircraft are permitted to fly through the
area but should exercise vigilance.
b. ATC ASSIGNED AIRSPACE. Airspace of defined vertical/lateral limits, assigned by ATC, for the purpose
of providing air traffic segregation between the specified activities being conducted within the assigned airspace
and other IFR air traffic. ATCAA locations and scheduled activation information can be found on the FAA SUA
website; a NOTAM will not be issued to announce the activation of this airspace.
Other Airspace Areas 3−5−11
AIM2/20/258/7/25 AIM
Chapter 4. Air Traffic Control
Section 1. Services Available to Pilots
4−1−1. Air Route Traffic Control Centers
Centers are established primarily to provide air traffic service to aircraft operating on IFR flight plans within
controlled airspace, and principally during the en route phase of flight.
4−1−2. Control Towers
Towers have been established to provide for a safe, orderly and expeditious flow of traffic on and in the vicinity
of an airport. When the responsibility has been so delegated, towers also provide for the separation of IFR aircraft
in the terminal areas.
REFERENCE−
AIM, Para 5−4−3, Approach Control.
4−1−3. Flight Service Stations
Flight Service Stations (FSSs) are air traffic facilities that provide pilot briefings, flight plan processing, en route
flight advisories, search and rescue services, and assistance to lost aircraft and aircraft in emergency situations.
FSSs also relay ATC clearances, process Notices to Airmen, and broadcast aviation weather and aeronautical
information. In Alaska, designated FSSs also take weather observations, and provide Airport Advisory Services
(AAS).
4−1−4. Recording and Monitoring
a. Calls to air traffic control (ATC) facilities (ARTCCs, Towers, FSSs, Central Flow, and Operations Centers)
over radio and ATC operational telephone lines (lines used for operational purposes such as controller
instructions, briefings, opening and closing flight plans, issuance of IFR clearances and amendments, counter
hijacking activities, etc.) may be monitored and recorded for operational uses such as accident investigations,
accident prevention, search and rescue purposes, specialist training and evaluation, and technical evaluation and
repair of control and communications systems.
b. Where the public access telephone is recorded, a beeper tone is not required. In place of the “beep” tone
the FCC has substituted a mandatory requirement that persons to be recorded be given notice they are to be
recorded and give consent. Notice is given by this entry, consent to record is assumed by the individual placing
a call to the operational facility.
4−1−5. Communications Release of IFR Aircraft Landing at an Airport Without an Operating
Control Tower
Aircraft operating on an IFR flight plan, landing at an airport without an operating control tower will be advised
to change to the airport advisory frequency when direct communications with ATC are no longer required.
Towers and centers do not have nontower airport traffic and runway in use information. The instrument approach
may not be aligned with the runway in use; therefore, if the information has not already been obtained, pilots
should make an expeditious change to the airport advisory frequency when authorized.
REFERENCE−
AIM, Para 5−4−4, Advance Information on Instrument Approach.
4−1−6. Pilot Visits to Air Traffic Facilities
Pilots are encouraged to participate in local pilot/air traffic control outreach activities. However, due to security
and workload concerns, requests for air traffic facility visits may not always be approved. Therefore, visit
Services Available to Pilots 4−1−1
AIM 2/20/25
requests should be submitted through the air traffic facility as early as possible. Pilots should contact the facility
and advise them of the number of persons in the group, the time and date of the proposed visit, and the primary
interest of the group. The air traffic facility will provide further instructions if a request can be approved.
REFERENCE−
F AA Order 1600.69, F AA Facility Security Management Program.
4−1−7. Operation Rain Check
Operation Rain Check is a program designed and managed by local air traffic control facility management. Its
purpose is to familiarize pilots and aspiring pilots with the ATC system, its functions, responsibilities and
benefits.
REFERENCE−
F AA Order JO 7210.3, Para 4−2−2, Pilot Education.
F AA Order 1600.69, F AA Facility Security Management Program.
4−1−8. Approach Control Service for VFR Arriving Aircraft
a. Numerous approach control facilities have established programs for arriving VFR aircraft to contact
approach control for landing information. This information includes: wind, runway, and altimeter setting at the
airport of intended landing. This information may be omitted if contained in the Automatic Terminal Information
Service (ATIS) broadcast and the pilot states the appropriate ATIS code.
NOTE−
Pilot use of “have numbers” does not indicate receipt of the ATIS broadcast. In addition, the controller will provide traffic
advisories on a workload permitting basis.
b. Such information will be furnished upon initial contact with concerned approach control facility. The pilot
will be requested to change to the tower frequency at a predetermined time or point, to receive further landing
information.
c. Where available, use of this procedure will not hinder the operation of VFR flights by requiring excessive
spacing between aircraft or devious routing.
d. Compliance with this procedure is not mandatory but pilot participation is encouraged.
REFERENCE−
AIM, Para 4−1−18, Terminal Radar Services for VFR Aircraft.
NOTE−
Approach control services for VFR aircraft are normally dependent on ATC radar. These services are not available during
periods of a radar outage.
4−1−9. Traffic Advisory Practices at Airports Without Operating Control Towers
(See TBL 4−1−1.)
a. Airport Operations Without Operating Control Tower
1. There is no substitute for alertness while in the vicinity of an airport. It is essential that pilots be alert and
look for other traffic and exchange traffic information when approaching or departing an airport without an
operating control tower. This is of particular importance since other aircraft may not have communication
capability or, in some cases, pilots may not communicate their presence or intentions when operating into or out
of such airports. To achieve the greatest degree of safety, it is essential that:
(a) All radio−equipped aircraft transmit/receive on a common frequency identified for the purpose of
airport advisories; and
(b) Pilots use the correct airport name, as identified in appropriate aeronautical publications, to reduce
the risk of confusion when communicating their position, intentions, and/or exchanging traffic information.
2. An airport may have a full or part-time tower or FSS located on the airport, a full or part-time UNICOM
station or no aeronautical station at all. There are three ways for pilots to communicate their intention and obtain
Services Available to Pilots 4−1−2
2/20/25 AIM
airport/traffic information when operating at an airport that does not have an operating tower: by communicating
with an FSS, a UNICOM operator, or by making a self-announce broadcast.
NOTE−
FSS airport advisories are available only in Alaska.
3. Many airports are now providing completely automated weather, radio check capability and airport
advisory information on an automated UNICOM system. These systems offer a variety of features, typically
selectable by microphone clicks, on the UNICOM frequency. Availability of the automated UNICOM will be
published in the Chart Supplement and approach charts.
b. Communicating on a Common Frequency
1. The key to communicating at an airport without an operating control tower is selection of the correct
common frequency. The acronym CTAF which stands for Common Traffic Advisory Frequency, is synonymous
with this program. A CTAF is a frequency designated for the purpose of carrying out airport advisory practices
while operating to or from an airport without an operating control tower. The CTAF may be a UNICOM,
MULTICOM, FSS, or tower frequency and is identified in appropriate aeronautical publications.
NOTE−
FSS frequencies are available only in Alaska.
Services Available to Pilots 4−1−3
AIM 2/20/25
TBL 4−1−1
Summary of Recommended Communication Procedures
Communication/Broadcast Procedures
Facility at Airport Frequency Use Outbound Inbound
Practice
Instrument
Approach
1. UNICOM (No Tower or
FSS)
Communicate with UNICOM
station on published CTAF
frequency (122.7; 122.8; 122.725;
122.975; or 123.0). If unable to
contact UNICOM station, use
self-announce procedures on
CTAF.
Before taxiing and
before taxiing on
the runway for
departure.
10 miles out.
Entering
downwind, base,
and final. Leaving
the runway.
2. No Tower, FSS, or
UNICOM
Self-announce on MULTICOM
frequency 122.9.
Before taxiing and
before taxiing on
the runway for
departure.
10 miles out.
Entering
downwind, base,
and final. Leaving
the runway.
Departing final
approach fix
(name) or on final
approach segment
inbound.
3. No Tower in operation,
FSS open (Alaska only)
Communicate with FSS on CTAF
frequency.
Before taxiing and
before taxiing on
the runway for
departure.
10 miles out.
Entering
downwind, base,
and final. Leaving
the runway.
Approach com-
pleted/terminated.
4. FSS Closed (No Tower) Self-announce on CTAF. Before taxiing and
before taxiing on
the runway for
departure.
10 miles out.
Entering
downwind, base,
and final. Leaving
the runway.
5. Tower or FSS not in
operation
Self-announce on CTAF. Before taxiing and
before taxiing on
the runway for
departure.
10 miles out.
Entering
downwind, base,
and final. Leaving
the runway.
6. Designated CTAF Area
(Alaska Only)
Self-announce on CTAF
designated on chart or Chart
Supplement Alaska.
Before taxiing and
before taxiing on
the runway for
departure until
leaving designated
area.
When entering
designated CTAF
area.
2. CTAF (Alaska Only). In Alaska, a CTAF may also be designated for the purpose of carrying out
advisory practices while operating in designated areas with a high volume of VFR traffic.
3. The CTAF frequency for a particular airport or area is contained in the Chart Supplement U.S., Chart
Supplement Alaska, Alaska Terminal Publication, Instrument Approach Procedure Charts, and Instrument
Departure Procedure (DP) Charts. Also, the CTAF frequency can be obtained by contacting any FSS. Use of the
appropriate CTAF, combined with a visual alertness and application of the following recommended good
operating practices, will enhance safety of flight into and out of all uncontrolled airports.
c. Recommended Traffic Advisory Practices
1. Pilots of inbound traffic should monitor and communicate as appropriate on the designated CTAF from
10 miles to landing. Pilots of departing aircraft should monitor/communicate on the appropriate frequency from
start-up, during taxi, and until 10 miles from the airport unless the CFRs or local procedures require otherwise.
2. Pilots of aircraft conducting other than arriving or departing operations at altitudes normally used by
arriving and departing aircraft should monitor/communicate on the appropriate frequency while within 10 miles
of the airport unless required to do otherwise by the CFRs or local procedures. Such operations include parachute
jumping/dropping, en route, practicing maneuvers, etc.
Services Available to Pilots 4−1−4
2/20/25 AIM
3. In Alaska, pilots of aircraft conducting other than arriving or departing operations in designated CTAF
areas should monitor/communicate on the appropriate frequency while within the designated area, unless
required to do otherwise by CFRs or local procedures. Such operations include parachute jumping/dropping, en
route, practicing maneuvers, etc.
REFERENCE−
AIM, Para 3−5−4, Parachute Jump Aircraft Operations
d. Airport Advisory/Information Services Provided by a FSS
1. There are two advisory type services provided at selected airports.
(a) Local Airport Advisory (LAA) is available only in Alaska and provided at airports that have a FSS
physically located on the airport, which does not have a control tower or where the tower is operated on a
part−time basis. The CTAF for LAA airports is disseminated in the appropriate aeronautical publications.
(b) Remote Airport Information Service (RAIS) is provided in support of special events at nontowered
airports by request from the airport authority.
2. In communicating with a CTAF FSS, check the airport’s automated weather and establish two −way
communications before transmitting outbound/inbound intentions or information. An inbound aircraft should
initiate contact approximately 10 miles from the airport, reporting aircraft identification and type, altitude,
location relative to the airport, intentions (landing or over flight), possession of the automated weather, and
request airport advisory or airport information service. A departing aircraft should initiate contact before taxiing,
reporting aircraft identification and type, VFR or IFR, location on the airport, intentions, direction of take−off,
possession of the automated weather, and request airport advisory or information service. Also, report intentions
before taxiing onto the active runway for departure. If you must change frequencies for other service after initial
report to FSS, return to FSS frequency for traffic update.
(a) Inbound
EXAMPLE−
Vero Beach radio, Centurion Six Niner Delta Delta is ten miles south, two thousand, landing Vero Beach. I have the
automated weather, request airport advisory.
(b) Outbound
EXAMPLE−
Vero Beach radio, Centurion Six Niner Delta Delta, ready to taxi to runway 22, VFR, departing to the southwest. I have the
automated weather, request airport advisory.
3. Airport advisory service includes wind direction and velocity, favored or designated runway, altimeter
setting, known airborne and ground traffic, NOTAMs, airport taxi routes, airport traffic pattern information, and
instrument approach procedures. These elements are varied so as to best serve the current traffic situation. Some
airport managers have specified that under certain wind or other conditions designated runways be used. Pilots
should advise the FSS of the runway they intend to use.
CAUTION−
All aircraft in the vicinity of an airport may not be in communication with the FSS.
e. Information Provided by Aeronautical Advisory Stations (UNICOM)
1. UNICOM is a nongovernment air/ground radio communication station which may provide airport
information at public use airports where there is no tower or FSS.
2. On pilot request, UNICOM stations may provide pilots with weather information, wind direction, the
recommended runway, or other necessary information. If the UNICOM frequency is designated as the CTAF,
it will be identified in appropriate aeronautical publications.
f. Unavailability of Information from FSS or UNICOM
Should LAA by an FSS or Aeronautical Advisory Station UNICOM be unavailable, wind and weather
information may be obtainable from nearby controlled airports via Automatic Terminal Information Service
(ATIS) or Automated Weather Observing System (AWOS) frequency.
Services Available to Pilots 4−1−5
AIM 2/20/25
g. Self-Announce Position and/or Intentions
1. General. Self-announce is a procedure whereby pilots broadcast their position or intended flight activity
or ground operation on the designated CTAF. This procedure is used primarily at airports which do not have an
FSS on the airport. The self-announce procedure should also be used if a pilot is unable to communicate with
the FSS on the designated CTAF. Pilots stating, “Traffic in the area, please advise” is not a recognized
Self−Announce Position and/or Intention phrase and should not be used under any condition.
2. If an airport has a tower and it is temporarily closed, or operated on a part-time basis and there is no FSS
on the airport or the FSS is closed, use the CTAF to self-announce your position or intentions.
3. Where there is no tower, FSS, or UNICOM station on the airport, use MULTICOM frequency 122.9 for
self-announce procedures. Such airports will be identified in appropriate aeronautical information publications.
4. Straight−in Landings. The FAA discourages VFR straight −in approaches to landings due to the
increased risk of a mid−air collision. However, if a pilot chooses to execute a straight−in approach for landing
without entering the airport traffic pattern, the pilot should self−announce their position on the designated CTAF
approximately 8 to 10 miles from the airport and coordinate their straight−in approach and landing with other
airport traffic. Pilots executing a straight−in approach (IFR or VFR) do not have priority over other aircraft in
the traffic pattern, and must comply with the provisions of 14 CFR 91.113 (g), Right−of−way rules.
5. Traffic Pattern Operations. All traffic within a 10− mile radius of a non −towered airport or a
part−time−towered airport when the control tower is not operating, should monitor and communicate on the
designated CTAF when entering the traffic pattern. Pilots operating in the traffic pattern or on a straight −in
approach must be alert at all times to other aircraft in the pattern, or conducting straight −in approaches, and
communicate their position to avoid a possible traffic conflict. In the airport traffic pattern and while on
straight−in approaches to a runway, effective communication and a pilot’s responsibility to see−and−avoid are
essential mitigations to avoid a possible midair collision. In addition, following established traffic pattern
procedures eliminates excessive maneuvering at low altitudes, reducing the risk of loss of aircraft control.
REFERENCE−
F AA Advisory Circular (AC) 90−66, Non−Towered Airport Flight Operations.
6. Practice Approaches. Pilots conducting practice instrument approaches should be particularly alert for
other aircraft that may be departing in the opposite direction. When conducting any practice approach, regardless
of its direction relative to other airport operations, pilots should make announcements on the CTAF as follows:
(a) Departing the final approach fix, inbound (nonprecision approach) or departing the outer marker or
fix used in lieu of the outer marker, inbound (precision approach);
(b) Established on the final approach segment or immediately upon being released by ATC;
(c) Upon completion or termination of the approach; and
(d) Upon executing the missed approach procedure.
7. Departing aircraft should always be alert for arrival aircraft coming from the opposite direction.
8. Recommended self−announce broadcasts: It should be noted that aircraft operating to or from another
nearby airport may be making self−announce broadcasts on the same UNICOM or MULTICOM frequency. To
help identify one airport from another, the airport name should be spoken at the beginning and end of each
self−announce transmission. When referring to a specific runway, pilots should use the runway number and not
use the phrase “Active Runway.”
(a) Inbound
EXAMPLE−
Strawn traffic, Apache Two Two Five Zulu, (position), (altitude), (descending) or entering downwind/base/final (as
appropriate) runway one seven full stop, touch−and−go, Strawn.
Strawn traffic Apache Two Two Five Zulu clear of runway one seven Strawn.
(b) Outbound
Services Available to Pilots 4−1−6
2/20/25 AIM
EXAMPLE−
Strawn traffic, Queen Air Seven One Five Five Bravo (location on airport) taxiing to runway two six Strawn.
Strawn traffic, Queen Air Seven One Five Five Bravo departing runway two six. Departing the pattern to the (direction),
climbing to (altitude) Strawn.
(c) Practice Instrument Approach
EXAMPLE−
Strawn traffic, Cessna Two One Four Three Quebec (position from airport) inbound descending through (altitude) practice
(name of approach) approach runway three five Strawn.
Strawn traffic, Cessna Two One Four Three Quebec practice (type) approach completed or terminated runway three five
Strawn.
h. UNICOM Communications Procedures
1. In communicating with a UNICOM station, the following practices will help reduce frequency
congestion, facilitate a better understanding of pilot intentions, help identify the location of aircraft in the traffic
pattern, and enhance safety of flight:
(a) Select the correct UNICOM frequency.
(b) State the identification of the UNICOM station you are calling in each transmission.
(c) Speak slowly and distinctly.
(d) Report approximately 10 miles from the airport, reporting altitude, and state your aircraft type,
aircraft identification, location relative to the airport, state whether landing or overflight, and request wind
information and runway in use.
(e) Report on downwind, base, and final approach.
(f) Report leaving the runway.
2. Recommended UNICOM phraseologies:
(a) Inbound
PHRASEOLOGY−
FREDERICK UNICOM CESSNA EIGHT ZERO ONE TANGO FOXTROT 10 MILES SOUTHEAST DESCENDING
THROUGH (altitude) LANDING FREDERICK, REQUEST WIND AND RUNWAY INFORMATION FREDERICK.
FREDERICK TRAFFIC CESSNA EIGHT ZERO ONE TANGO FOXTROT ENTERING DOWNWIND/BASE/ FINAL (as
appropriate) FOR RUNWAY ONE NINER (full stop/touch−and−go) FREDERICK.
FREDERICK TRAFFIC CESSNA EIGHT ZERO ONE TANGO FOXTROT CLEAR OF RUNWAY ONE NINER
FREDERICK.
(b) Outbound
PHRASEOLOGY−
FREDERICK UNICOM CESSNA EIGHT ZERO ONE TANGO FOXTROT (location on airport) TAXIING TO RUNWAY
ONE NINER, REQUEST WIND AND TRAFFIC INFORMATION FREDERICK.
FREDERICK TRAFFIC CESSNA EIGHT ZERO ONE TANG O FOXTROT DEP ARTING RUNWAY ONE NINER.
“REMAINING IN THE P ATTERN” OR “DEP ARTING THE P ATTERN TO THE (direction) (as appropriate)”
FREDERICK.
4−1−10. IFR Approaches/Ground Vehicle Operations
a. IFR Approaches. When operating in accordance with an IFR clearance and ATC approves a change to
the advisory frequency, make an expeditious change to the CTAF and employ the recommended traffic advisory
procedures.
b. Ground Vehicle Operation. Airport ground vehicles equipped with radios should monitor the CTAF
frequency when operating on the airport movement area and remain clear of runways/taxiways being used by
aircraft. Radio transmissions from ground vehicles should be confined to safety-related matters.
Services Available to Pilots 4−1−7
AIM 2/20/25
c. Radio Control of Airport Lighting Systems. Whenever possible, the CTAF will be used to control airport
lighting systems at airports without operating control towers. This eliminates the need for pilots to change
frequencies to turn the lights on and allows a continuous listening watch on a single frequency. The CTAF is
published on the instrument approach chart and in other appropriate aeronautical information publications.
4−1−11. Designated UNICOM/MULTICOM Frequencies
Frequency use
a. The following listing depicts UNICOM and MULTICOM frequency uses as designated by the Federal
Communications Commission (FCC). (See TBL 4−1−2.)
TBL 4−1−2
Unicom/Multicom Frequency Usage
Use Frequency
Airports without an operating control tower. 122.700
122.725
122.800
122.975
123.000
123.050
123.075
(MULTICOM FREQUENCY) Activities of a
temporary, seasonal, emergency nature or
search and rescue, as well as, airports with no
tower, FSS, or UNICOM.
122.900
(MULTICOM FREQUENCY) Forestry
management and fire suppression, fish and
game management and protection, and
environmental monitoring and protection.
122.925
Airports with a control tower or FSS on airport. 122.950
NOTE−
1. In some areas of the country, frequency interference may be encountered from nearby airports using the same UNICOM
frequency. Where there is a problem, UNICOM operators are encouraged to develop a “least interference” frequency
assignment plan for airports concerned using the frequencies designated for airports without operating control towers.
UNICOM licensees are encouraged to apply for UNICOM 25 kHz spaced channel frequencies. Due to the extremely limited
number of frequencies with 50 kHz channel spacing, 25 kHz channel spacing should be implemented. UNICOM licensees
may then request FCC to assign frequencies in accordance with the plan, which FCC will review and consider for approval.
2. Wind direction and runway information may not be available on UNICOM frequency 122.950.
b. The following listing depicts other frequency us es as designated by the Federal Communications
Commission (FCC). (See TBL 4−1−3.)
Services Available to Pilots 4−1−8
2/20/25 AIM
TBL 4−1−3
Other Frequency Usage Designated by FCC
Use Frequency
Air-to-air communication
(private fixed wing aircraft).
122.750
Helicopter air−to−air communications; air
traffic control operations.
123.025
Aviation instruction, Glider, Hot Air Balloon
(not to be used for advisory service).
123.300
123.500
Assignment to flight test land and aircraft stations
(not for air−to−air communication except for
those aircraft operating in an oceanic FIR).
123.4001
123.4502
1This frequency is available only to itinerant stations that have a requirement to be periodically transferred to various
locations.
2Mobile station operations on these frequencies are limited to an area within 320 km (200 mi) of an associated flight test
land station.
4−1−12. Use of UNICOM for ATC Purposes
UNICOM service may be used for ATC purposes, only under the following circumstances:
a. Revision to proposed departure time.
b. Takeoff, arrival, or flight plan cancellation time.
c. ATC clearance, provided arrangements are made between the ATC facility and the UNICOM licensee to
handle such messages.
4−1−13. Automatic Terminal Information Service (ATIS)
a. ATIS is the continuous broadcast of recorded noncontrol information in selected high activity terminal
areas. Its purpose is to improve controller effectiveness and to relieve frequency congestion by automating the
repetitive transmission of essential but routine information. The information is continuously broadcast over a
discrete VHF radio frequency or the voice portion of a local NA V AID. Arrival ATIS transmissions on a discrete
VHF radio frequency are engineered according to the individual facility requirements, which would normally
be a protected service volume of 20 NM to 60 NM from the ATIS site and a maximum altitude of 25,000 feet
AGL. In the case of a departure ATIS, the protected service volume cannot exceed 5 NM and 100 feet AGL. At
most locations, ATIS signals may be received on the surface of the airport, but local conditions may limit the
maximum ATIS reception distance and/or altitude. Pilots are urged to cooperate in the ATIS program as it relieves
frequency congestion on approach control, ground control, and local control frequencies. The Chart Supplement
indicates airports for which ATIS is provided.
b. ATIS information includes:
1. Airport/facility name
2. Phonetic letter code
3. Time of the latest weather sequence (UTC)
4. Weather information consisting of:
(a) Wind direction and velocity
(b) Visibility
(c) Obstructions to vision
Services Available to Pilots 4−1−9
AIM 2/20/25
(d) Present weather consisting of: sky condition, temperature, dew point, altimeter, a density altitude
advisory when appropriate, and other pertinent remarks included in the official weather observation
5. Instrument approach and runway in use.
The ceiling/sky condition, visibility, and obstructions to vision may be omitted from the ATIS broadcast if the
ceiling is above 5,000 feet and the visibility is more than 5 miles. The departure runway will only be given if
different from the landing runway except at locations having a separate ATIS for departure. The broadcast may
include the appropriate frequency and instructions for VFR arrivals to make initial contact with approach control.
Pilots of aircraft arriving or departing the terminal area can receive the continuous ATIS broadcast at times when
cockpit duties are least pressing and listen to as many repeats as desired. ATIS broadcast must be updated upon
the receipt of any official hourly and special weather. A new recording will also be made when there is a change
in other pertinent data such as runway change, instrument approach in use, etc.
EXAMPLE−
Dulles International information Sierra. One four zero zero zulu. Wind three five zero at eight. Visibility one zero. Ceiling
four thousand five hundred broken. Temperature three four. Dew point two eight. Altimeter three zero one zero. ILS runway
one right approach in use. Departing runway three zero. Advise on initial contact you have information sierra.
c. Pilots should listen to ATIS broadcasts whenever ATIS is in operation.
d. Pilots should notify controllers on initial contact that they have received the ATIS broadcast by repeating
the alphabetical code word appended to the broadcast.
EXAMPLE−
“Information Sierra received.”
e. When a pilot acknowledges receipt of the ATIS broadcast, controllers may omit those items contained in
the broadcast if they are current. Rapidly changing conditions will be issued by ATC and the ATIS will contain
words as follows:
EXAMPLE−
“Latest ceiling/visibility/altimeter/wind/(other conditions) will be issued by approach control/tower .”
NOTE−
The absence of a sky condition or ceiling and/or visibility on ATIS indicates a sky condition or ceiling of 5,000 feet or above
and visibility of 5 miles or more. A remark may be made on the broadcast, “the weather is better than 5000 and 5,” or the
existing weather may be broadcast.
f. Controllers will issue pertinent information to pilots who do not acknowledge receipt of a broadcast or who
acknowledge receipt of a broadcast which is not current.
g. To serve frequency limited aircraft, FSSs are equipped to transmit on the omnirange frequency at most en
route VORs used as ATIS voice outlets. Such communication interrupts the ATIS broadcast. Pilots of aircraft
equipped to receive on other FSS frequencies are encouraged to do so in order that these override transmissions
may be kept to an absolute minimum.
h. While it is a good operating practice for pilots to make use of the ATIS broadcast where it is available, some
pilots use the phrase “have numbers” in communications with the control tower. Use of this phrase means that
the pilot has received wind, runway, and altimeter information ONLY and the tower does not have to repeat this
information. It does not indicate receipt of the ATIS broadcast and should never be used for this purpose.
4−1−14. Automatic Flight Information Service (AFIS) − Alaska FSSs Only
a. AFIS is the continuous broadcast of recorded non−control information at airports in Alaska where an FSS
provides local airport advisory service. Its purpose is to improve FSS specialist efficiency by reducing frequency
congestion on the local airport advisory frequency.
1. The AFIS broadcast will automate the repetitive transmission of essential but routine information (for
example, weather, favored runway, braking action, airport NOTAMs, etc.). The information is continuously
broadcast over a discrete VHF radio frequency (usually the ASOS frequency).
Services Available to Pilots 4−1−10
AIM2/20/258/7/25 AIM
2. Use of AFIS is not mandatory, but pilots who choose to utilize two−way radio communications with the
FSS are urged to listen to AFIS, as it relieves frequency congestion on the local airport advisory frequency. AFIS
broadcasts are updated upon receipt of any official hourly and special weather, and changes in other pertinent
data.
3. When a pilot acknowledges receipt of the AFIS br oadcast, FSS specialists may omit those items
contained in the broadcast if they are current. When rapidly changing conditions exist, the latest ceiling,
visibility, altimeter, wind or other conditions may be omitted from the AFIS and will be issued by the FSS
specialist on the appropriate radio frequency.
EXAMPLE−
“Kotzebue information ALPHA. One six five five zulu. Wind, two one zero at five; visibility two, fog; ceiling one hundred
overcast; temperature minus one two, dew point minus one four; altimeter three one zero five. Altimeter in excess of three
one zero zero, high pressure altimeter setting procedures are in effect. Favored runway two six. Weather in Kotzebue surface
area is below V−F−R minima − an ATC clearance is required. Contact Kotzebue Radio on 123.6 for traffic advisories and
advise intentions. Notice to Airmen, Hotham NDB out of service. Transcribed Weather Broadcast out of service. Advise on
initial contact you have ALPHA.”
NOTE−
The absence of a sky condition or ceiling and/or visibility on Alaska FSS AFIS indicates a sky condition or ceiling of 5,000
feet or above and visibility of 5 miles or more. A remark may be made on the broadcast, “the weather is better than 5000
and 5.”
b. Pilots should listen to Alaska FSSs AFIS broadcasts whenever Alaska FSSs AFIS is in operation.
NOTE−
Some Alaska FSSs are open part time and/or seasonally.
c. Pilots should notify controllers on initial contact that they have received the Alaska FSSs AFIS broadcast
by repeating the phonetic alphabetic letter appended to the broadcast.
EXAMPLE−
“Information Alpha received.”
d. While it is a good operating practice for pilots to make use of the Alaska FSS AFIS broadcast where it is
available, some pilots use the phrase “have numbers” in communications with the FSS. Use of this phrase means
that the pilot has received wind, runway, and altimeter information ONLY and the Alaska FSS does not have to
repeat this information. It does not indicate receipt of the AFIS broadcast and should never be used for this
purpose.
4−1−15. Radar Traffic Information Service
This is a service provided by radar ATC facilities. Pilots receiving this service are advised of any radar target
observed on the radar display which may be in such proximity to the position of their aircraft or its intended route
of flight that it warrants their attention. This service is not intended to relieve the pilot of the responsibility for
continual vigilance to see and avoid other aircraft.
a. Purpose of the Service
1. The issuance of traffic information as observed on a radar display is based on the principle of assisting
and advising a pilot that a particular radar target’s position and track indicates it may intersect or pass in such
proximity to that pilot’s intended flight path that it warrants attention. This is to alert the pilot to the traffic, to
be on the lookout for it, and thereby be in a better position to take appropriate action should the need arise.
2. Pilots are reminded that the surveillance radar used by ATC does not provide altitude information unless
the aircraft is equipped with Mode C and the radar facility is capable of displaying altitude information.
b. Provisions of the Service
1. Many factors, such as limitations of the radar, volume of traffic, controller workload and communications
frequency congestion, could prevent the controller from providing this service. Controllers possess complete
discretion for determining whether they are able to provide or continue to provide this service in a specific case.
Services Available to Pilots 4−1−11
AIM 2/20/25
The controller’s reason against providing or continuing to provide the service in a particular case is not subject
to question nor need it be communicated to the pilot. In other words, the provision of this service is entirely
dependent upon whether controllers believe they are in a position to provide it. Traffic information is routinely
provided to all aircraft operating on IFR flight plans except when the pilot declines the service, or the pilot is
operating within Class A airspace. Traffic information may be provided to flights not operating on IFR flight
plans when requested by pilots of such flights.
NOTE−
Radar ATC facilities normally display and monitor both primary and secondary radar as well as ADS −B, except that
secondary radar or ADS−B may be used as the sole display source in Class A airspace, and under some circumstances
outside of Class A airspace (beyond primary coverage and in en route areas where only secondary and/or ADS −B is
available). Secondary radar and/or ADS−B may also be used outside Class A airspace as the sole display source when the
primary radar is temporarily unusable or out of service. Pilots in contact with the affected ATC facility are normally advised
when a temporary outage occurs; i.e., “primary radar out of service; traffic advisories available on transponder or ADS−B
aircraft only.” This means simply that only aircraft that have transponders and ADS−B installed and in use will be depicted
on ATC displays when the primary and/or secondary radar is temporarily out of service.
2. When receiving VFR radar advisory service, pilots should monitor the assigned frequency at all times.
This is to preclude controllers’ concern for radio failure or emergency assistance to aircraft under the controller’s
jurisdiction. VFR radar advisory service does not include vectors away from conflicting traffic unless requested
by the pilot. When advisory service is no longer desired, advise the controller before changing frequencies and
then change your transponder code to 1200, if applicable. Pilots should also inform the controller when changing
VFR cruising altitude. Except in programs where radar service is automatically terminated, the controller will
advise the aircraft when radar is terminated.
NOTE−
Participation by VFR pilots in formal programs implemented at certain terminal locations constitutes pilot request. This
also applies to participating pilots at those locations where arriving VFR flights are encouraged to make their first contact
with the tower on the approach control frequency.
c. Issuance of Traffic Information. Traffic information will include the following concerning a target
which may constitute traffic for an aircraft that is:
1. Radar identified
(a) Azimuth from the aircraft in terms of the 12 hour clock, or
(b) When rapidly maneuvering civil test or military aircraft prevent accurate issuance of traffic as in (a)
above, specify the direction from an aircraft’s position in terms of the eight cardinal compass points (N, NE, E,
SE, S, SW, W, NW). This method must be terminated at the pilot’s request.
(c) Distance from the aircraft in nautical miles;
(d) Direction in which the target is proceeding; and
(e) Type of aircraft and altitude if known.
EXAMPLE−
Traffic 10 o’clock, 3 miles, west-bound (type aircraft and altitude, if known, of the observed traffic). The altitude may be
known, by means of Mode C, but not verified with the pilot for accuracy. (To be valid for separation purposes by ATC, the
accuracy of Mode C readouts must be verified. This is usually accomplished upon initial entry into the radar system by a
comparison of the readout to pilot stated altitude, or the field elevation in the case of continuous readout being received from
an aircraft on the airport.) When necessary to issue traffic advisories containing unverified altitude information, the
controller will issue the indicated altitude of the aircraft. The pilot may upon receipt of traffic information, request a vector
(heading) to avoid such traffic. The vector will be provided to the extent possible as determined by the controller provided
the aircraft to be vectored is within the airspace under the jurisdiction of the controller .
2. Not radar identified
(a) Distance and direction with respect to a fix;
(b) Direction in which the target is proceeding; and
Services Available to Pilots 4−1−12
2/20/25 AIM
(c) Type of aircraft and altitude if known.
EXAMPLE−
Traffic 8 miles south of the airport northeast−bound, (type aircraft and altitude if known).
d. The examples depicted in the following figures point out the possible error in the position of this traffic
when it is necessary for a pilot to apply drift correction to maintain this track. This error could also occur in the
event a change in course is made at the time radar traffic information is issued.
FIG 4−1−1
Induced Error in Position of Traffic
WIND
TRACK TRACK
(A) (B)
EXAMPLE−
In FIG 4−1−1 traffic information would be issued to the pilot of aircraft “A” as 12 o’clock. The actual position of the traffic
as seen by the pilot of aircraft “A” would be 2 o’clock. Traffic information issued to aircraft “B” would also be given as
12 o’clock, but in this case, the pilot of “B” would see the traffic at 10 o’clock.
FIG 4−1−2
Induced Error in Position of Traffic
TRACK
(C)
(D)
WIND TRACK
EXAMPLE−
In FIG 4−1−2 traffic information would be issued to the pilot of aircraft “C” as 2 o’clock. The actual position of the traffic
as seen by the pilot of aircraft “C” would be 3 o’clock. Traffic information issued to aircraft “D” would be at an 11 o’clock
position. Since it is not necessary for the pilot of aircraft “D” to apply wind correction (crab) to remain on track, the actual
position of the traffic issued would be correct. Since the radar controller can only observe aircraft track (course) on the radar
display, traffic advisories are issued accordingly, and pilots should give due consideration to this fact when looking for
reported traffic.
4−1−16. Safety Alert
A safety alert will be issued to pilots of aircraft being controlled by ATC if the controller is aware the aircraft
is at an altitude which, in the controller’s judgment, places the aircraft in unsafe proximity to terrain, obstructions
or other aircraft. The provision of this service is contingent upon the capability of the controller to have an
awareness of a situation involving unsafe proximity to terrain, obstructions and uncontrolled aircraft. The
issuance of a safety alert cannot be mandated, but it can be expected on a reasonable, though intermittent basis.
Once the alert is issued, it is solely the pilot’s prerogative to determine what course of action, if any, to take. This
procedure is intended for use in time critical situations where aircraft safety is in question. Noncritical situations
should be handled via the normal traffic alert procedures.
a. Terrain or Obstruction Alert
1. Controllers will immediately issue an alert to the pilot of an aircraft under their control when they
recognize that the aircraft is at an altitude which, in their judgment, may be in an unsafe proximity to
Services Available to Pilots 4−1−13
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terrain/obstructions. The primary method of detecting unsafe proximity is through Mode C automatic altitude
reports.
EXAMPLE−
Low altitude alert Cessna Three Four Juliett, check your altitude immediately. And if the aircraft is not yet on final approach,
the MVA (MEA/MIA/MOCA) in your area is six thousand.
2. Most En Route and Terminal radar facilities have an automated function which, if operating, alerts
controllers when a tracked Mode C equipped aircraft under their control is below or is predicted to be below a
predetermined minimum safe altitude. This function, called Minimum Safe Altitude Warning (MSAW), is
designed solely as a controller aid in detecting potentially unsafe aircraft proximity to terrain/obstructions. The
radar facility will, when MSAW is operating, provide MSAW monitoring for all aircraft with an operating Mode
C altitude encoding transponder that are tracked by the system and are:
(a) Operating on an IFR flight plan; or
(b) Operating VFR and have requested MSAW monitoring.
NOTE−
Pilots operating VFR may request MSAW monitoring if their aircraft are equipped with Mode C transponders.
EXAMPLE−
Apache Three Three Papa request MSAW monitoring.
3. Due to the lack of terrain and obstacle clearance data, accurate automation databases may not be available
for providing MSAW information to aircraft overflying Mexico and Canada. Air traffic facilities along the
United States/Mexico/Canada borders may have MSAW computer processing inhibited where accurate terrain
data is not available.
b. Aircraft Conflict Alert.
1. Controllers will immediately issue an alert to the pilot of an aircraft under their control if they are aware
of another aircraft which is not under their control, at an altitude which, in the controller’s judgment, places both
aircraft in unsafe proximity to each other. With the alert, when feasible, the controller will offer the pilot the
position of the traffic if time permits and an alternate course(s) of action. Any alternate course(s) of action the
controller may recommend to the pilot will be predicated only on other traffic being worked by the controller.
EXAMPLE−
American Three, traffic alert, (position of traffic, if time permits), advise you turn right/left heading (degrees) and/or
climb/descend to (altitude) immediately.
4−1−17. Radar Assistance to VFR Aircraft
a. Radar equipped FAA ATC facilities provide radar assistance and navigation service (vectors) to VFR
aircraft provided the aircraft can communicate with the facility, are within radar coverage, and can be radar
identified.
b. Pilots should clearly understand that authorization to proceed in accordance with such radar navigational
assistance does not constitute authorization for the pilot to violate CFRs. In effect, assistance provided is on the
basis that navigational guidance information issued is advisory in nature and the job of flying the aircraft safely,
remains with the pilot.
c. In many cases, controllers will be unable to determine if flight into instrument conditions will result from
their instructions. To avoid possible hazards resulting from being vectored into IFR conditions, pilots should
keep controllers advised of the weather conditions in which they are operating and along the course ahead.
d. Radar navigation assistance (vectors) may be initiated by the controller when one of the following
conditions exist:
1. The controller suggests the vector and the pilot concurs.
2. A special program has been established and vectoring service has been advertised.
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3. In the controller’s judgment the vector is necessary for air safety.
e. Radar navigation assistance (vectors) and other radar derived information may be provided in response to
pilot requests. Many factors, such as limitations of radar, volume of traffic, communications frequency,
congestion, and controller workload could prevent the controller from providing it. Controllers have complete
discretion for determining if they are able to provide the service in a particular case. Their decision not to provide
the service in a particular case is not subject to question.
4−1−18. Terminal Radar Services for VFR Aircraft
a. Basic Radar Service:
1. In addition to the use of radar for the control of IFR aircraft, all commissioned radar facilities provide
the following basic radar services for VFR aircraft:
(a) Safety alerts.
(b) Traffic advisories.
(c) Limited radar vectoring (on a workload permitting basis).
(d) Sequencing at locations where procedures have been established for this purpose and/or when
covered by a Letter of Agreement.
NOTE−
When the stage services were developed, two basic radar services (traffic advisories and limited vectoring) were identified
as “Stage I.” This definition became unnecessary and the term “Stage I” was eliminated from use. The term “Stage II” has
been eliminated in conjunction with the airspace reclassification, and sequencing services to locations with local procedures
and/or letters of agreement to provide this service have been included in basic services to VFR aircraft. These basic services
will still be provided by all terminal radar facilities whether they include Class B, Class C, Class D or Class E airspace.
“Stage III” services have been replaced with “Class B” and “TRSA” service where applicable.
2. Vectoring service may be provided when requested by the pilot or with pilot concurrence when suggested
by ATC.
3. Pilots of arriving aircraft should contact approach control on the publicized frequency and give their
position, altitude, aircraft call sign, type aircraft, radar beacon code (if transponder equipped), destination, and
request traffic information.
4. Approach control will issue wind and runway, except when the pilot states “have numbers” or this
information is contained in the ATIS broadcast and the pilot states that the current ATIS information has been
received. Traffic information is provided on a workload permitting basis. Approach control will specify the time
or place at which the pilot is to contact the tower on local control frequency for further landing information. Radar
service is automatically terminated and the aircraft need not be advised of termination when an arriving VFR
aircraft receiving radar services to a tower−controlled airport where basic radar service is provided has landed,
or to all other airports, is instructed to change to tower or advisory frequency. (See FAA Order JO 7110.65, Air
Traffic Control, paragraph 5−1−9, Radar Service Termination.)
5. Sequencing for VFR aircraft is available at certain terminal locations (see locations listed in the Chart
Supplement). The purpose of the service is to adjust the flow of arriving VFR and IFR aircraft into the traffic
pattern in a safe and orderly manner and to provide radar traffic information to departing VFR aircraft. Pilot
participation is urged but is not mandatory. Traffic information is provided on a workload permitting basis.
Standard radar separation between VFR or between VFR and IFR aircraft is not provided.
(a) Pilots of arriving VFR aircraft should initiate radio contact on the publicized frequency with approach
control when approximately 25 miles from the airport at which sequencing services are being provided. On initial
contact by VFR aircraft, approach control will assume that sequencing service is requested. After radar contact
is established, the pilot may use pilot navigation to enter the traffic pattern or, depending on traffic conditions,
approach control may provide the pilot with routings or vectors necessary for proper sequencing with other
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participating VFR and IFR traffic en route to the airport. When a flight is positioned behind a preceding aircraft
and the pilot reports having that aircraft in sight, the pilot will be instructed to follow the preceding aircraft. THE
ATC INSTRUCTION TO FOLLOW THE PRECEDING AIRCRAFT DOES NOT AUTHORIZE THE PILOT
TO COMPLY WITH ANY ATC CLEARANCE OR IN STRUCTION ISSUED TO THE PRECEDING
AIRCRAFT. If other “nonparticipating” or “local” aircraft are in the traffic pattern, the tower will issue a landing
sequence. If an arriving aircraft does not want radar service, the pilot should state “NEGATIVE RADAR
SERVICE” or make a similar comment, on initial contact with approach control.
(b) Pilots of departing VFR aircraft are encouraged to request radar traffic information by notifying
ground control, or where applicable, clearance delivery, on initial contact with their request and proposed
direction of flight.
EXAMPLE−
Xray ground control, November One Eight Six, Cessna One Seventy Two, ready to taxi, VFR southbound at 2,500, have
information bravo and request radar traffic information.
NOTE−
Following takeoff, the tower will advise when to contact departure control.
(c) Pilots of aircraft transiting the area and in radar contact/communication with approach control will
receive traffic information on a controller workload permitting basis. Pilots of such aircraft should give their
position, altitude, aircraft call sign, aircraft type, radar beacon code (if transponder equipped), destination, and/or
route of flight.
b. TRSA Service (Radar Sequencing and Separation Service for VFR Aircraft in a TRSA).
1. This service has been implemented at certain terminal locations. The service is advertised in the Chart
Supplement. The purpose of this service is to provide separation between all participating VFR aircraft and all
IFR aircraft operating within the airspace defined as the Terminal Radar Service Area (TRSA). Pilot participation
is urged but is not mandatory.
2. If any aircraft does not want the service, the pilot should state “NEGATIVE TRSA SERVICE” or make
a similar comment, on initial contact with approach control or ground control, as appropriate.
3. TRSAs are depicted on sectional aeronautical charts and listed in the Chart Supplement.
4. While operating within a TRSA, pilots are provided TRSA service and separation as prescribed in this
paragraph. In the event of a radar outage, separation and sequencing of VFR aircraft will be suspended as this
service is dependent on radar. The pilot will be advised that the service is not available and issued wind, runway
information, and the time or place to contact the tower. Traffic information will be provided on a workload
permitting basis.
5. Visual separation is used when prevailing conditions permit and it will be applied as follows:
(a) When a VFR flight is positioned behind a preceding aircraft and the pilot reports having that aircraft
in sight, the pilot will be instructed by A TC to follow the preceding aircraft. Radar service will be continued to
the runway. THE ATC INSTRUCTION TO FOLLOW THE PRECEDING AIRCRAFT DOES NOT
AUTHORIZE THE PILOT TO COMPLY WITH ANY ATC CLEARANCE OR INSTRUCTION ISSUED TO
THE PRECEDING AIRCRAFT.
(b) If other “nonparticipating” or “local” aircraft are in the traffic pattern, the tower will issue a landing
sequence.
(c) Departing VFR aircraft may be asked if they can visually follow a preceding departure out of the
TRSA. The pilot will be instructed to follow the other aircraft provided that the pilot can maintain visual contact
with that aircraft.
6. Participating VFR aircraft will be separated from IFR and other participating VFR aircraft by one of the
following:
(a) 500 feet vertical separation.
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(b) Visual separation.
(c) Target resolution (a process to ensure that correlated radar targets do not touch).
7. Participating pilots operating VFR in a TRSA:
(a) Must maintain an altitude when assigned by ATC unless the altitude assignment is to maintain at or
below a specified altitude. ATC may assign altitudes for separation that do not conform to 14 CFR
section 91.159. When the altitude assignment is no longer needed for separation or when leaving the TRSA, the
instruction will be broadcast, “RESUME APPROPRIATE VFR ALTITUDES.” Pilots must then return to an
altitude that conforms to 14 CFR section 91.159 as soon as practicable.
(b) When not assigned an altitude, the pilot should coordinate with ATC prior to any altitude change.
8. Within the TRSA, traffic information on observed but unidentified targets will, to the extent possible,
be provided to all IFR and participating VFR aircraft. The pilot will be vectored upon request to avoid the
observed traffic, provided the aircraft to be vectored is within the airspace under the jurisdiction of the controller.
9. Departing aircraft should inform ATC of their intended destination and/or route of flight and proposed
cruising altitude.
10. ATC will normally advise participating VFR aircraft when leaving the geographical limits of the TRSA.
Radar service is not automatically terminated with this advisory unless specifically stated by the controller.
c. Class C Service. This service provides, in addition to basic radar service, approved separation between
IFR and VFR aircraft, and sequencing of VFR arrivals to the primary airport.
d. Class B Service. This service provides, in addition to basic radar service, approved separation of aircraft
based on IFR, VFR, and/or weight, and sequencing of VFR arrivals to the primary airport(s).
e. PILOT RESPONSIBILITY. THESE SERVICES ARE NOT TO BE INTERPRETED AS RELIEVING
PILOTS OF THEIR RESPONSIBILITIES TO SEE AND AVOID OTHER TRAFFIC OPERATING IN BASIC
VFR WEATHER CONDITIONS, TO ADJUST THEIR OPERATIONS AND FLIGHT PATH AS
NECESSARY TO PRECLUDE SERIOUS WAKE ENCOUNTERS, TO MAINTAIN APPROPRIATE
TERRAIN AND OBSTRUCTION CLEARANCE, OR TO REMAIN IN WEATHER CONDITIONS EQUAL
TO OR BETTER THAN THE MINIMUMS REQUI RED BY 14 CFR SECTION 91.155. WHENEVER
COMPLIANCE WITH AN ASSIGNED ROUTE, HE ADING AND/OR ALTITUDE IS LIKELY TO
COMPROMISE PILOT RESPONSIBILITY RESPE CTING TERRAIN AND OBSTRUCTION CLEAR -
ANCE, VORTEX EXPOSURE, AND WEATHER MINIMUMS, APPROACH CONTROL SHOULD BE SO
ADVISED AND A REVISED CLEARANCE OR INSTRUCTION OBTAINED.
f. ATC services for VFR aircraft participating in terminal radar services are dependent on ATC radar. Services
for VFR aircraft are not available during periods of a radar outage. The pilot will be advised when VFR services
are limited or not available.
NOTE−
Class B and Class C airspace are areas of regulated airspace. The absence of ATC radar does not negate the requirement
of an ATC clearance to enter Class B airspace or two way radio contact with ATC to enter Class C airspace.
4−1−19. Tower En Route Control (TEC)
a. TEC is an A TC program to provide a service to aircraft proceeding to and from metropolitan areas. It links
designated Approach Control Areas by a network of identified routes made up of the existing airway structure
of the National Airspace System. The FAA initiated an expanded TEC program to include as many facilities as
possible. The program’s intent is to provide an overflow resource in the low altitude system which would enhance
ATC services. A few facilities have historically allowed turbojets to proceed between certain city pairs, such as
Milwaukee and Chicago, via tower en route and these locations may continue this service. However, the
expanded TEC program will be applied, generally, for nonturbojet aircraft operating at and below 10,000 feet.
The program is entirely within the approach control airspace of multiple terminal facilities. Essentially, it is for
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relatively short flights. Participating pilots are encouraged to use TEC for flights of two hours duration or less.
If longer flights are planned, extensive coordination may be required within the multiple complex which could
result in unanticipated delays.
b. Pilots requesting TEC are subject to the same delay factor at the destination airport as other aircraft in the
ATC system. In addition, departure and en route delays may occur depending upon individual facility workload.
When a major metropolitan airport is incurring significant delays, pilots in the TEC program may want to
consider an alternative airport experiencing no delay.
c. There are no unique requirements upon pilots to use the TEC program. Normal flight plan filing procedures
will ensure proper flight plan processing. Pilots should include the acronym “TEC” in the remarks section of the
flight plan when requesting tower en route control.
d. All approach controls in the system may not operate up to the maximum TEC altitude of 10,000 feet. IFR
flight may be planned to any satellite airport in proximity to the major primary airport via the same routing.
4−1−20. Transponder and ADS−B Out Operation
a. General
1. Pilots should be aware that proper application of transponder and ADS −B operating procedures will
provide both VFR and IFR aircraft with a higher degree of safety while operating on the ground and airborne.
Transponder/ADS−B panel designs differ; therefore, a pilot should be thoroughly familiar with the operation of
their particular equipment to maximize its full potential. ADS−B Out, and transponders with altitude reporting
mode turned ON (Mode C or S), substantially increase the capability of surveillance systems to see an aircraft.
This provides air traffic controllers, as well as pilots of suitably equipped aircraft (TCAS and ADS −B In),
increased situational awareness and the ability to identify potential traffic conflicts. Even VFR pilots who are
not in contact with ATC will be afforded greater protection from IFR aircraft and VFR aircraft that are receiving
traffic advisories. Nevertheless, pilots should never relax their visual scanning for other aircraft, and should
include the ADS−B In display (if equipped) in their normal traffic scan.
2. Air Traffic Control Radar Beacon System (ATCRBS) is similar to and compatible with military coded
radar beacon equipment. Civil Mode A is identical to military Mode 3.
3. Transponder and ADS-B operations on the ground. Civil and military aircraft should operate with
the transponder in the altitude reporting mode (consult the aircraft’s flight manual to determine the specific
transponder position to enable altitude reporting) and ADS−B Out transmissions enabled at all airports, any time
the aircraft is positioned on any portion of the airport movement area. This includes all defined taxiways and
runways. Pilots must pay particular attention to ATIS and airport diagram notations, General Notes (included
on airport charts), and comply with directions pertaining to transponder and ADS-B usage. Generally, these
directions are:
(a) Departures. Select the transponder mode which allows altitude reporting and enable ADS-B during
pushback or taxi-out from parking spot. Select TA or TA/RA (if equipped with TCAS) when taking the active
runway.
(b) Arrivals. If TCAS equipped, deselect TA or TA/RA upon leaving the active runway, but continue
transponder and ADS−B transmissions in the altitude reporting mode. Select STBY or OFF for transponder and
ADS−B upon arriving at the aircraft’s parking spot or gate.
4. Transponder and ADS-B Operations While Airborne.
(a) Unless otherwise requested by ATC, aircraft equipped with an ATC transponder maintained in
accordance with 14 CFR section 91.413 MUST operate with this equipment on the appropriate Mode 3/A code,
or other code as assigned by ATC, and with altitude reporting enabled whenever in controlled airspace. If
practicable, aircraft SHOULD operate with the transponder enabled in uncontrolled airspace.
(b) Aircraft equipped with ADS−B Out MUST operate with this equipment in the transmit mode at all
times, unless otherwise requested by ATC.
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5. Transponder and ADS−B Operation Under Visual Flight Rules (VFR).
(a) Unless otherwise instructed by an ATC facility, adjust transponder/ADS−B to reply on Mode 3/A
Code 1200 regardless of altitude.
(b) When required to operate their transponder/ADS−B, pilots must always operate that equipment with
altitude reporting enabled unless otherwise instructed by ATC or unless the installed equipment has not been
tested and calibrated as required by 14 CFR section 91.217. If deactivation is required, turn off altitude reporting.
(c) When participating in a VFR standard formation flight that is not receiving ATC services, only the
lead aircraft should operate its transponder and ADS −B Out and squawk code 1203. Once established in
formation, all other aircraft should squawk standby and disable ADS−B transmissions.
NOTE−
1. If the formation flight is receiving ATC services, pilots can expect ATC to direct all non−lead aircraft to STOP Squawk,
and should not do so until instructed.
2. Firefighting aircraft not in contact with ATC may squawk 1255 in lieu of 1200 while en route to, from, or within the
designated firefighting area(s).
3. VFR aircraft flying authorized SAR missions for the USAF or USCG may be advised to squawk 1277 in lieu of 1200 while
en route to, from, or within the designated search area.
4. VFR gliders should squawk 1202 in lieu of 1200.
REFERENCE−
F AA Order JO 7110.66, National Beacon Code Allocation Plan (NBCAP).
6. A pilot on an IFR flight who elects to cancel the IFR flight plan prior to reaching their destination, should
adjust the transponder/ADS−B according to VFR operations.
7. If entering a U.S. OFFSHORE AIRSPACE AREA from outside the U.S., the pilot should advise on first
radio contact with a U.S. radar ATC facility that such equipment is available by adding “transponder” or
“ADS−B” (if equipped) to the aircraft identification.
8. It should be noted by all users of ATC transponders and ADS −B Out systems that the surveillance
coverage they can expect is limited to “line of sight” with ground radar and ADS−B radio sites. Low altitude or
aircraft antenna shielding by the aircraft itself may result in reduced range or loss of aircraft contact. Though
ADS−B often provides superior reception at low altitudes, poor coverage from any surveillance system can be
improved by climbing to a higher altitude.
NOTE−
Pilots should refer to AIM, paragraph 4 −5−7, Automatic Dependent Surveillance − Broadcast (ADS−B) Services, for a
complete description of operating limitations and procedures.
b. Transponder/ADS−B Code Designation
1. For A TC to utilize one of the 4096 discrete codes, a four−digit code designation will be used; for example,
code 2102 will be expressed as “TWO ONE ZERO TWO.”
NOTE−
Circumstances may occasionally require ATC to assign a non−discrete code; i.e., a code ending in “00.”
REFERENCE−
F AA Order JO 7110.66, National Beacon Code Allocation Plan (NBCAP).
c. Automatic Altitude Reporting
1. Most transponders (Modes C and S) and all ADS−B Out systems are capable of automatic altitude
reporting. This system converts aircraft altitude in 100 −foot increments to coded digital information that is
transmitted to the appropriate surveillance facility as well as to ADS−B In and TCAS systems.
2. Adjust the transponder/ADS−B to reply on the Mode 3/A code specified by ATC and with altitude
reporting enabled, unless otherwise directed by ATC or unless the altitude reporting equipment has not been
tested and calibrated as required by 14 CFR section 91.217. If deactivation is required by ATC, turn off the
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altitude reporting feature of your transponder/ADS−B. An instruction by ATC to “STOP ALTITUDE SQUAWK,
ALTITUDE DIFFERS BY (number of feet) FEET,” may be an indication that the transmitted altitude
information is incorrect, or that the aircraft’s altimeter setting is incorrect. While an incorrect altimeter setting
has no effect on the transmitted altitude information, it will cause the aircraft to fly at a true altitude different from
the assigned altitude. When a controller indicates that an altitude readout is invalid, the pilot should verify that
the aircraft altimeter is set correctly.
NOTE−
Altitude encoders are preset at standard atmospheric pressure. Local altimeter correction is applied by the surveillance
facility before the altitude information is presented to ATC.
3. Pilots should report exact altitude or flight level to the nearest hundred foot increment when establishing
initial contact with an ATC facility. Exact altitude or flight level reports on initial contact provide ATC with
information that is required prior to using automatically reported altitude information for separation purposes.
This will significantly reduce altitude verification requests.
d. IDENT Feature
Transponder/ADS−B Out equipment must be operated only as specified by ATC. Activate the “IDENT” feature
only when requested by ATC.
e. Code Changes
1. When making routine code changes, pilots should avoid inadvertent selection of Codes 7500, 7600 or
7700 thereby causing momentary false alarms at automated ground facilities. For example, when switching from
Code 2700 to Code 7200, switch first to 2200 then to 7200, NOT to 7700 and then 7200. This procedure applies
to nondiscrete Code 7500 and all discrete codes in the 7600 and 7700 series (i.e., 7600−7677, 7700−7777) which
will trigger special indicators in automated facilities. Only nondiscrete Code 7500 will be decoded as the hijack
code.
2. Under no circumstances should a pilot of a civil aircraft operate the transponder on Code 7777. This code
is reserved for military interceptor operations.
3. Military pilots operating VFR or IFR within restricted/warning areas should adjust their transponders to
Code 4000 unless another code has been assigned by ATC.
f. Mode C Transponder and ADS−B Out Requirements
1. Specific details concerning requirements to carry and operate Mode C transponders and ADS−B Out, as
well as exceptions and ATC authorized deviations from those requirements, are found in 14 CFR sections 91.215,
91.225, and 99.13.
2. In general, the CFRs require aircraft to be equipped with an operable Mode C transponder and ADS−B
Out when operating:
(a) In Class A, Class B, or Class C airspace areas;
(b) Above the ceiling and within the lateral boundaries of Class B or Class C airspace up to 10,000 feet
MSL;
(c) Class E airspace at and above 10,000 feet MSL within the 48 contiguous states and the District of
Columbia, excluding the airspace at and below 2,500 feet AGL;
(d) Within 30 miles of a Class B airspace primary airport, below 10,000 feet MSL (commonly referred
to as the “Mode C Veil”);
(e) For ADS−B Out: Class E airspace at and above 3,000 feet MSL over the Gulf of America from the
coastline of the United States out to 12 nautical miles.
NOTE−
The airspace described in (e) above is specified in 14 CFR § 91.225 for ADS−B Out requirements. However, 14 CFR § 91.215
does not include this airspace for ATC transponder requirements.
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(f) Transponder and ADS−B Out requirements do not apply to any aircraft that was not originally
certificated with an electrical system, or that has not subsequently been certified with such a system installed,
including balloons and gliders. These aircraft may conduct operations without a transponder or ADS −B Out
when operating:
(1) Outside any Class B or Class C airspace area; and
(2) Below the altitude of the ceiling of a Class B or Class C airspace area designated for an airport, or
10,000 feet MSL, whichever is lower.
3. 14 CFR section 99.13 requires all aircraft flying into, within, or across the contiguous U.S. ADIZ be
equipped with a Mode C or Mode S transponder. Balloons, gliders and aircraft not equipped with an
engine−driven electrical system are excepted from this requirement.
REFERENCE−
AIM, Chapter 5, Section 6, National Security and Interception Procedures.
4. Pilots must ensure that their aircraft transponder/ADS−B is operating on an appropriate ATC−assigned
VFR/IFR code with altitude reporting enabled when operating in such airspace. If in doubt about the operational
status of either feature of your transponder while airborne, contact the nearest ATC facility or FSS and they will
advise you what facility you should contact for determining the status of your equipment.
5. In−flight requests for “immediate” deviation from the transponder requirements may be approved by
controllers only for failed equipment, and only when the flight will continue IFR or when weather conditions
prevent VFR descent and continued VFR flight in airspace not affected by the CFRs. All other requests for
deviation should be made at least 1 hour before the proposed operation by contacting the nearest Flight Service
or Air Traffic facility in person or by telephone. The nearest ARTCC will normally be the controlling agency
and is responsible for coordinating requests involving deviations in other ARTCC areas.
6. In−flight requests for “immediate” deviation from the ADS−B Out requirements may be approved by
ATC only for failed equipment, and may be accommodated based on workload, alternate surveillance
availability, or other factors. All other requests for deviation must be made at least 1 hour before the proposed
operation, following the procedures contained in Advisory Circular (AC) 90− 114, Automatic Dependent
Surveillance−Broadcast Operations.
g. Cooperative Surveillance Phraseology. Air traffic controllers, both civil and military, will use the
following phraseology when referring to operation of cooperative ATC surveillance equipment. Except as noted,
the following ATC instructions do not apply to military transponders operating in other than Mode 3/A/C/S.
1. SQUAWK (number). Operate radar beacon transponder/ADS −B on designated code with altitude
reporting enabled.
2. IDENT. Engage the “IDENT” feature (military I/P) of the transponder/ADS−B.
3. SQUAWK (number) AND IDENT. Operate transponder/ADS−B on specified code with altitude
reporting enabled, and engage the “IDENT” (military I/P) feature.
4. SQUAWK STANDBY. Switch transponder/ADS−B to standby position.
5. SQUAWK NORMAL. Resume normal transponder/ADS−B operation on previously assigned code.
(Used after “SQUAWK STANDBY ,” or by military after specific transponder tests).
6. SQUAWK ALTITUDE. Activate Mode C with automatic altitude reporting.
7. STOP ALTITUDE SQUAWK. Turn off automatic altitude reporting.
8. STOP SQUAWK (Mode in use). Stop transponder and ADS−B Out transmissions, or switch off only
specified mode of the aircraft transponder (military).
9. SQUAWK MA YDAY. Operate transponder/ADS−B in the emergency position (Mode A Code 7700 for
civil transponder. Mode 3 Code 7700 and emergency feature for military transponder.)
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10. SQUAWK VFR. Operate radar beacon transponder/ADS−B on Code 1200 in the Mode A/3, or other
appropriate VFR code, with altitude reporting enabled.
4−1−21. Airport Reservation Operations and Special Traffic Management Programs
This section describes procedures for obtaining required airport reservations at airports designated by the FAA
and for airports operating under Special Traffic Management Programs.
a. Slot Controlled Airports.
1. The FAA may adopt rules to require advance reservations for unscheduled operations at certain airports.
In addition to the information in the rules adopted by the FAA, a listing of the airports and relevant information
will be maintained on the FAA website www.fly.faa.gov/ecvrs.
2. The FAA has established an Airport Reservation Office (ARO) to receive and process reservations for
unscheduled flights at the slot controlled airports. The ARO uses the Enhanced Computer V oice Reservation
System (e−CVRS) to allocate reservations. Reservations will be available beginning 72 hours in advance of the
operation at the slot controlled airport. Standby lists are not maintained. Flights with declared emergencies do
not require reservations. Refer to the website for the current listing of slot controlled airports, limitations, and
reservation procedures.
3. For more detailed information on operations and reservation procedures at a Slot Controlled Airport,
please see 14 CFR part 93, Subpart K – High Density Traffic Airports.
b. Special Traffic Management Programs (STMP).
1. Special programs may be established when a location requires special traffic handling to accommodate
above normal traffic demand (for example, NFL Super Bowl, EAA AirVenture Oshkosh, SUN ’n FUN
Aerospace Expo) or reduced airport capacity (for example, significant airport runway closures for airport
construction). The special programs may remain in effect until the problem has been resolved or until local traffic
management procedures can handle the volume and a need for special handling no longer exists.
2. If an STMP is used to accommodate a special event, a domestic notice will be issued relaying the website
address: www.fly.faa.gov/estmp. Domestic notice information includes: what airports are included in the STMP,
the dates and times reservations are required, the time limits for reservation requests, the point of contact for
reservations, and any other instructions.
c. Making Reservations. Detailed information and User Instruction Guides for using the Web reservation
systems are available on the websites for the slot controlled airports (e −CVRS), www.fly.faa.gov/ecvrs; and
STMPs (e−STMP), www.fly.faa.gov/estmp.
NOTE−
Users may contact the ARO at (540) 422−4246 if they have a problem with their reservation.
d. Prior Permission Required (PPR).
1. A PPR may be required at locations where air traffic demand does not require an STMP, but operations
may be impacted by on−airport activity or by a nearby event.
2. Events that may require a PPR include, but are not limited to:
(a) Construction on or near an active runway requiring time to remove personnel and equipment.
(b) Limited ramp space for parking aircraft.
(c) Snow removal at airports without an operating control tower.
(d) General aviation operations into military airports.
3. Pilots are responsible for coordinating operations related to the PPR. Controllers may be aware of the
PPR, but they do not enforce or otherwise oversee compliance. Operations contrary to a PPR could result in a
safety hazard to persons or property on the ground.
Services Available to Pilots 4−1−22
AIM2/20/251/22/26 AIM
4. PPRs are disseminated via NOTAM or published in the airport remarks section of the Chart Supplement
and typically includes a phone number or frequency to coordinate operations. An identification number may be
issued that is to be included in the Remarks section of the flight plan. Major airports with PPRs are listed on the
FAA’s National Airspace System Status website (https://nasstatus.faa.gov).
4−1−22. Requests for Waivers and Authorizations from Title 14, Code of Federal
Regulations (14 CFR)
a. Requests for a Certificate of Waiver or Authorization (FAA Form 7711−2), or requests for renewal of a
waiver or authorization, may be accepted by any FAA facility and will be forwarded, if necessary, to the
appropriate office having waiver authority.
b. The grant of a Certificate of Waiver or Authorization from 14 CFR constitutes relief from specific
regulations, to the degree and for the period of time specified in the certificate, and does not waive any state law
or local ordinance. Should the proposed operations conflict with any state law or local ordinance, or require
permission of local authorities or property owners, it is the applicant’s responsibility to resolve the matter. The
holder of a waiver is responsible for compliance with the terms of the waiver and its provisions.
c. A waiver may be canceled at any time by the Administrator, the person authorized to grant the waiver, or
the representative designated to monitor a specific operation. In such case either written notice of cancellation,
or written confirmation of a verbal cancellation will be provided to the holder.
4−1−23. Weather Systems Processor
The Weather Systems Processor (WSP) was developed for use in the National Airspace System to provide
weather processor enhancements to selected Airport Surveillance Radar (ASR)−9 facilities. The WSP provides
Air Traffic with warnings of hazardous wind shear and microbursts. The WSP also provides users with terminal
area 6−level weather, storm cell locations and movement, as well as the location and predicted future position
and intensity of wind shifts that may affect airport operations.
Services Available to Pilots 4−1−23
2/20/25 AIM
Section 2. Radio Communications Phraseology
and Techniques
4−2−1. General
a. Radio communications are a critical link in the ATC system. The link can be a strong bond between pilot
and controller or it can be broken with surprising speed and disastrous results. Discussion herein provides basic
procedures for new pilots and also highlights safe operating concepts for all pilots.
b. The single, most important thought in pilot-controller communications is understanding. It is essential,
therefore, that pilots acknowledge each radio communication with ATC by using the appropriate aircraft call
sign. Brevity is important, and contacts should be kept as brief as possible, but controllers must know what you
want to do before they can properly carry out their control duties. And you, the pilot, must know exactly what
the controller wants you to do. Since concise phraseology may not always be adequate, use whatever words are
necessary to get your message across. Pilots are to maintain vigilance in monitoring air traffic control radio
communications frequencies for potential traffic conflicts with their aircraft especially when operating on an
active runway and/or when conducting a final approach to landing.
c. All pilots will find the Pilot/Controller Glossary very helpful in learning what certain words or phrases
mean. Good phraseology enhances safety and is the mark of a professional pilot. Jargon, chatter, and “CB” slang
have no place in ATC communications. The Pilot/Controller Glossary is the same glossary used in FAA Order
JO 7110.65, Air Traffic Control. We recommend that it be studied and reviewed from time to time to sharpen
your communication skills.
4−2−2. Radio Technique
a. Listen before you transmit. Many times you can get the information you want through ATIS or by
monitoring the frequency. Except for a few situations where some frequency overlap occurs, if you hear someone
else talking, the keying of your transmitter will be futile and you will probably jam their receivers causing them
to repeat their call. If you have just changed frequencies, pause, listen, and make sure the frequency is clear.
b. Think before keying your transmitter. Know what you want to say and if it is lengthy; e.g., a flight plan
or IFR position report, jot it down.
c. The microphone should be very close to your lips and after pressing the mike button, a slight pause may
be necessary to be sure the first word is transmitted. Speak in a normal, conversational tone.
d. When you release the button, wait a few seconds before calling again. The controller or FSS specialist may
be jotting down your number, looking for your flight plan, transmitting on a different frequency, or selecting the
transmitter for your frequency.
e. Be alert to the sounds or the lack of sounds in your receiver. Check your volume, recheck your frequency,
and make sure that your microphone is not stuck in the transmit position. Frequency blockage can, and has,
occurred for extended periods of time due to unintentional transmitter operation. This type of interference is
commonly referred to as a “stuck mike,” and controllers may refer to it in this manner when attempting to assign
an alternate frequency. If the assigned frequency is completely blocked by this type of interference, use the
procedures described for en route IFR radio frequency outage to establish or reestablish communications with
ATC.
f. Be sure that you are within the performance range of your radio equipment and the ground station
equipment. Remote radio sites do not always transmit and receive on all of a facility’s available frequencies,
particularly with regard to VOR sites where you can hear but not reach a ground station’s receiver. Remember
that higher altitudes increase the range of VHF “line of sight” communications.
Radio Communications Phraseology 4−2−1
AIM 2/20/25
4−2−3. Contact Procedures
a. Initial Contact.
1. The terms initial contact or initial callup means the first radio call you make to a given facility or the first
call to a different controller or FSS specialist within a facility. Use the following format:
(a) Name of the facility being called;
(b) Your full aircraft identification as filed in the flight plan or as discussed in paragraph 4−2−4, Aircraft
Call Signs;
(c) When operating on an airport surface, state your position.
(d) The type of message to follow or your request if it is short; and
(e) The word “Over” if required.
EXAMPLE−
1. “New York Radio, Mooney Three One One Echo.”
2. “Columbia Ground, Cessna Three One Six Zero Foxtrot, south ramp, I−F−R Memphis.”
3. “Miami Center, Baron Five Six Three Hotel, request V−F−R traffic advisories.”
2. Many FSSs are equipped with Remote Communications Outlets (RCOs) and can transmit on the same
frequency at more than one location. The frequencies available at specific locations are indicated on charts above
FSS communications boxes. To enable the specialist to utilize the correct transmitter, advise the location and the
frequency on which you expect a reply.
EXAMPLE−
St. Louis FSS can transmit on frequency 122.3 at either Farmington, Missouri, or Decatur, Illinois, if you are in the vicinity
of Decatur, your callup should be “Saint Louis radio, Piper Six Niner Six Yankee, receiving Decatur One Two Two Point
Three.”
3. If radio reception is reasonably assured, inclusion of your request, your position or altitude, and the
phrase “(ATIS) Information Charlie received” in the initial contact helps decrease radio frequency congestion.
Use discretion; do not overload the controller with information unneeded or superfluous. If you do not get a
response from the ground station, recheck your radios or use another transmitter, but keep the next contact short.
EXAMPLE−
“Atlanta Center, Duke Four One Romeo, request V−F−R traffic advisories, Twenty Northwest Rome, seven thousand five
hundred, over.”
b. Initial Contact When Your Transmitting and Receiving Frequencies are Different.
1. If you are attempting to establish contact with a ground station and you are receiving on a different
frequency than that transmitted, indicate the VOR name or the frequency on which you expect a reply. Most FSSs
and control facilities can transmit on several VOR stations in the area. Use the appropriate FSS call sign as
indicated on charts.
EXAMPLE−
New York FSS transmits on the Kennedy, the Hampton, and the Calverton VORTACs. If you are in the Calverton area, your
callup should be “New York radio, Cessna Three One Six Zero Foxtrot, receiving Calverton V−O−R, over.”
2. If the chart indicates FSS frequencies above the VORTAC or in the FSS communications boxes, transmit
or receive on those frequencies nearest your location.
3. When unable to establish contact and you wish to call any ground station, use the phrase “ANY RADIO
(tower) (station), GIVE CESSNA THREE ONE SI X ZERO FOXTROT A CALL ON (frequency) OR
(V−O−R).” If an emergency exists or you need assistance, so state.
c. Subsequent Contacts and Responses to Callup from a Ground Facility.
Use the same format as used for the initial contact except you should state your message or request with the callup
in one transmission. The ground station name and the word “Over” may be omitted if the message requires an
4−2−2 Radio Communications Phraseology
2/20/25 AIM
obvious reply and there is no possibility for misunderstandings. You should acknowledge all callups or
clearances unless the controller or FSS specialist advises otherwise. There are some occasions when controllers
must issue time-critical instructions to other aircraft, and they may be in a position to observe your response,
either visually or on radar. If the situation demands your response, take appropriate action or immediately advise
the facility of any problem. Acknowledge with your aircraft identification, either at the beginning or at the end
of your transmission, and one of the words “Wilco,” “Roger,” “Affirmative,” “Negative,” or other appropriate
remarks; e.g., “PIPER TWO ONE FOUR LIMA, ROGER.” If you have been receiving services; e.g., VFR traffic
advisories and you are leaving the area or changing frequencies, advise the ATC facility and terminate contact.
d. Acknowledgement of Frequency Changes.
1. When advised by ATC to change frequencies, acknowledge the instruction. If you select the new
frequency without an acknowledgement, the controller’s workload is increased because there is no way of
knowing whether you received the instruction or have had radio communications failure.
2. At times, a controller/specialist may be working a sector with multiple frequency assignments. In order
to eliminate unnecessary verbiage and to free the controller/specialist for higher priority transmissions, the
controller/specialist may request the pilot “(Identification), change to my frequency 134.5.” This phrase should
alert the pilot that the controller/specialist is only changing frequencies, not controller/specialist, and that initial
callup phraseology may be abbreviated.
EXAMPLE−
“United Two Twenty−Two on one three four point five” or “one three four point five, United Two Twenty−Two.”
e. Compliance with Frequency Changes.
When instructed by ATC to change frequencies, select the new frequency as soon as possible unless instructed
to make the change at a specific time, fix, or altitude. A delay in making the change could result in an untimely
receipt of important information. If you are instructed to make the frequency change at a specific time, fix, or
altitude, monitor the frequency you are on until reaching the specified time, fix, or altitudes unless instructed
otherwise by ATC.
REFERENCE−
AIM, Para 5−3−1, ARTCC Communications.
4−2−4. Aircraft Call Signs
a. Precautions in the Use of Call Signs.
1. Improper use of call signs can result in pilots executing a clearance intended for another aircraft. Call
signs should never be abbreviated on an initial contact or at any time when other aircraft call signs have similar
numbers/sounds or identical letters/number; e.g., Cessna 6132F, Cessna 1622F, Baron 123F, Cherokee 7732F,
etc.
EXAMPLE−
Assume that a controller issues an approach clearance to an aircraft at the bottom of a holding stack and an aircraft with
a similar call sign (at the top of the stack) acknowledges the clearance with the last two or three numbers of the aircraft’ s
call sign. If the aircraft at the bottom of the stack did not hear the clearance and intervene, flight safety would be affected,
and there would be no reason for either the controller or pilot to suspect that anything is wrong. This kind of “human factors”
error can strike swiftly and is extremely difficult to rectify.
2. Pilots, therefore, must be certain that aircraft identification is complete and clearly identified before
taking action on an ATC clearance. ATC specialists will not abbreviate call signs of air carrier or other civil
aircraft having authorized call signs. ATC specialists may initiate abbreviated call signs of other aircraft by using
the prefix and the last three digits/letters of the aircraft identification after communications are established. The
pilot may use the abbreviated call sign in subseque nt contacts with the ATC specialist. When aware of
similar/identical call signs, ATC specialists will take action to minimize errors by emphasizing certain
numbers/letters, by repeating the entire call sign, by repeating the prefix, or by asking pilots to use a different
call sign temporarily. Pilots should use the phrase “VERIFY CLEARANCE FOR (your complete call sign)” if
doubt exists concerning proper identity.
Radio Communications Phraseology 4−2−3
AIM 2/20/25
3. Civil aircraft pilots should state the aircraft type, model or manufacturer’s name, followed by the
digits/letters of the registration number. When the aircraft manufacturer’s name or model is stated, the prefix “N”
is dropped; e.g., Aztec Two Four Six Four Alpha.
EXAMPLE−
1. Bonanza Six Five Five Golf.
2. Breezy Six One Three Romeo Experimental (omit “Experimental” after initial contact).
4. Air Taxi or other commercial operators not having FAA authorized call signs should prefix their normal
identification with the phonetic word “Tango.”
EXAMPLE−
Tango Aztec Two Four Six Four Alpha.
5. Air carriers and commuter air carriers having FAA authorized call signs should identify themselves by
stating the complete call sign (using group form for the numbers) and the word “super” or “heavy” if appropriate.
EXAMPLE−
1. United Twenty−Five Heavy.
2. Midwest Commuter Seven Eleven.
6. Military aircraft use a variety of systems including serial numbers, word call signs, and combinations of
letters/numbers. Examples include Army Copter 48931; Air Force 61782; REACH 31792; Pat 157; Air Evac
17652; Navy Golf Alfa Kilo 21; Marine 4 Charlie 36, etc.
b. Air Ambulance Flights.
Because of the priority afforded air ambulance flights in the ATC system, extreme discretion is necessary when
using the term “MEDEV AC.” It is only intended for those missions of an urgent medical nature and to be utilized
only for that portion of the flight requiring priority handling. It is important for ATC to be aware of a flight’s
MEDEV AC status, and it is the pilot’s responsibility to ensure that this information is provided to ATC. ....
1. To receive priority handling from ATC, the pilot must verbally identify the flight in radio transmissions
by stating “MEDEV AC” followed by the FAA authorized call sign (ICAO 3LD, US Special, or local) or the
aircraft civil “N” registration numbers/letters.
EXAMPLE−
If the aircraft identification of the flight indicates DAL51, the pilot states “MEDEVAC Delta Fifty One.”
If the aircraft identification of the flight indicates MDSTR1, the pilot states “MEDEVAC Medstar One.”
If the aircraft identification of the flight indicates N123G or LN123G, the pilot states “MEDEVAC One Two Three Golf”.
2. If requested by the pilot, ATC will provide additional assistance (e.g., landline notifications) to expedite
ground handling of patients, vital organs, or urgently needed medical materials. When possible make these
requests to ATC via methods other than through ATC radio frequencies.
3. MEDEV AC flights may include:
(a) Civilian air ambulance flights responding to medical emergencies (e.g., first call to an accident scene,
carrying patients, organ donors, organs, or other urgently needed lifesaving medical material).
(b) Air carrier and air taxi flights responding to medical emergencies. The nature of these medical
emergency flights usually concerns the transportation of urgently needed lifesaving medical materials or vital
organs, but can include inflight medical emergencies. It is imperative that the company/pilot determine, by the
nature/urgency of the specific medical cargo, if priority ATC assistance is required.
4. When filing a flight plan, pilots may include “L” for MEDEV AC with the aircraft registration
letters/digits and/or include “MEDEVAC” in Item 11 (Remarks) of the flight plan or Item 18 (Other Information)
of an international flight plan. However, ATC will only use these flight plan entries for informational purposes
or as a visual indicator. ATC will only provide prio rity handling when the pilot verbally identifies the
“MEDEV AC” status of the flight as described in subparagraph b1 above.
4−2−4 Radio Communications Phraseology