AIRSPACE INFORMATION (Continued)
Miscellaneous Activity Areas
Aerobatic Practice Area
Glider Operations
Hang Glider Activity
Ultralight Activity
Unmanned Aircraft Activity
Parachute Jumping Area with Frequency
Space Launch Activity Area
Military Training Routes (MTR)
Helicopter Routes
Primary Route with Route
Name and Tower Frequency
Secondary Route
Transition Symbol
Reporting Points
Non-compulsory
Compulsory
Reporting Point Name
Foreign Airspace Note
Police Zones
Special Use Airspace
Only the airspace effective
below 18,000 feet MSL is
shown.
The type of area shall be
spelled out in large areas if
space permits.
One-way Route
Altitude Changeover Point
Recommended Altitudes
Maximum Altitude
Minimum Altitude
Recommended Altitude
FAA Chart Users’ Guide - VFR Chart Symbology - Helicopter Charts
Special Conservation Areas
National Park, Wildlife Refuge,
Primitive and Wilderness Areas, etc.
VFR Checkpoints
Underline indicates proper
name of VFR Checkpoint.
Obstruction
Above 299’ and below 1000’ AGL
1000’ and higher AGL
High-Intensity Obstruction Lights
High-intensity lights may operate
part-time or by proximity activation.
Navigation Data
NOAA Regulated National
Marine Sanctuary Designated
Areas
VFR Waypoints
Stand-Alone
Collocated with VFR Checkpoint
Collocated with VFR Checkpoint
& Reporting Point
Group Obstruction
Above 299’ and below 1000’ AGL
1000’ and higher AGL
Wind Turbine Farms
2894 UC
When highest wind turbine is
unverified, UC will be shown
after MSL value.
Maximum Elevation Figure (MEF)
(see VFR Terms tab for explanation)
AIRSPACE INFORMATION (Continued)
FAA Chart Users’ Guide - VFR Chart Symbology - Helicopter Charts
NAVIGATIONAL AND PROCEDURAL INFORMATION
Roads
Dual-Lane:
Divided Highways
Major Boulevards & Major Streets
Primary
Boundaries
International
State or Province
Power Transmission Lines
Prominent Pictorials
Landmarks
CULTURE
Railroads
Single Track
Double Track
Bridges
Populated Places
Built-up Areas
FAA Chart Users’ Guide - VFR Chart Symbology - Helicopter Charts
FAA Chart Users’ Guide - VFR Chart Symbology - Helicopter Charts
CARIBBEAN VFR AERONAUTICAL CHARTS (CAC)
FAA Chart Users’ Guide - Caribbean VFR Aeronautical Charts (CAC)
The Caribbean Charts are published as two VFR Charts:
Caribbean 1 (CAC-1) covers Southern Florida, Cuba,
Haiti and the Bahamas; Caribbean 2 (CAC-2) covers
Puerto Rico, Haiti, Dominican Republic, the Lesser
Antilles and Leeward Islands. Charts are updated every
56-day chart cycle.
Caribbean Charts are designed for VFR flights and
provide aeronautical and topographic information of the
Caribbean. The aeronautical information includes
airports, radio aids to navigation, Class airspace and
special use airspace in U.S. and major airports, and
radio aids to navigation in foreign areas. The topographic
information includes city tint, populated places, principal
roads, drainage patterns and shaded relief.
The chart symbols used on the
Caribbean Charts are similar to
those used in the Sectional and
Terminal Area Charts, the major
difference being in scale. The
Caribbean VFR Chart scale is
1:1,000,000 versus the Sectional
Chart Scale of 1:500,000 and
Terminal Area Chart Scale of
1:250,000. Chart symbology will
appear smaller on the Caribbean
VFR Charts.
Example from Caribbean 2 VFR
Aeronautical Chart
FAA Chart Users’ Guide - Caribbean VFR Aeronautical Charts (CAC)
U.S. Airspace depiction as shown on Visual Aeronautical Charts
AIRSPACE
FAA Chart Users’ Guide - Airspace
Excerpt from Detroit Sectional Chart
FAA Chart Users’ Guide - Airspace
SPORTING
EVENT
TFR SITE
CLASS E
with
SURFACE
FLOOR
CLASS C
INNER BOUNDARY
CLASS C
OUTER BOUNDARY
SPORTING
EVENT
TFR SITES
CLASS E
AIRSPACE
EXTENSION
with
SURFACE
FLOOR
MODE C
BOUNDARYCLASS D AIRSPACE
CLASS B
INTERNAL SECTOR
BOUNDARIES
CLASS B
OUTER
BOUNDARY
CLASS E
with
700’ AGL FLOOR
CLASS E
with
700’ AGL FLOOR
{
{
CLASS B
EXTENSIONS
CLASS B
EXTENSION
CLASS E
with
1200’ AGL
FLOOR
CLASS E
with
1200’ AGL
FLOOR
{
CLASS E
with
1200’ AGL
FLOOR
EXPLANATION OF IFR ENROUTE TERMS
FAA charts are prepared in accordance with specifications of the Interagency Air Committee (IAC), and are approved by
representatives of the Federal Aviation Administration and the Department of Defense (DoD). Some information on these
charts may only apply to military pilots.
The explanations of symbols used on Instrument Flight Rule (IFR) Enroute Charts and examples in this section are based
primarily on the IFR Enroute Low Altitude Charts. Other IFR products use similar symbols in various colors. The chart leg-
ends portray aeronautical symbols with a brief description of what each symbol depicts. This section provides more details
of the symbols and how they are used on IFR Enroute charts.
AIRPORTS
Operational airports are shown on IFR Enroute Charts.
Low Charts:
• All IAP Airports are shown on the Low Altitude Charts (US and Alaska).
• Non-IAP Airports are shown on the U.S. Low Altitude Charts (Contiguous US) have a minimum hard surface
runway of 3,000’.
• Non-IAP airports are shown on the U.S. Low Altitude Alaska Charts are show if the runway is 3000’ or longer,
hard or soft surface.
• Public heliports with an Instrument Approach Procedure (IAP) or requested by the FAA or DoD are depicted on
the IFR Enroute Low Altitude Charts.
• Seaplane bases requested by the FAA or DoD are depicted on the IFR Enroute Low Altitude Charts.
On IFR Enroute Low Altitude Charts, airport tabulation is provided that identifies airport names, IDs and the panels they
are located on.
High Charts:
• Airports shown on the U.S. High Enroute Charts (Contiguous US) have a minimum hard surface runway of 5000’.
• Airports shown on the U.S. High Enroute Alaska Charts have a minimum hard surface runway of 4000’.
Charted airports are classified according to the following criteria:
LOW/HIGH ALTITUDE
Blue - Airports with an Instrument Approach Procedure and/or RADAR MINIMA published in the high altitude DoD
Flight Information Publications (FLIPs)
Green - Airports that have an approved Instrument Approach Procedure and/or RADAR MINIMA published in
either the U.S. Terminal Procedures Publications (TPPs) or the DoD FLIPs
Brown - Airports without a published Instrument Approach Procedure or RADAR MINIMA
Black - Foreign airports
Airports are plotted at their true geographic position.
Airports are identified by the airport name. In the case of military airports, Air Force Base (AFB), Naval Air Station (NAS),
Naval Air Facility (NAF), Marine Corps Air Station (MCAS), Army Air Field (AAF), etc., the abbreviated letters appear as
part of the airport name.
FAA Chart Users’ Guide - IFR Enroute Terms
Airports marked "Pvt" immediately following the airport name are not for public use, but otherwise meet the criteria for
charting as specified above.
Runway length is the length of the longest active runway (including displaced thresholds but excluding overruns) and is
shown to the nearest 100 feet using 70 feet as the division point; e.g., a runway of 8,070' is labeled 81. The following run-
way compositions (materials) constitute a hard-surfaced runway: asphalt, bitumen, chip seal, concrete, and tar macadam.
Runways that are not hard-surfaced have a small letter "s" following the runway length, indicating a soft surface.
AIRPORT DATA DEPICTION
Low Altitude
1. Airport elevation given in feet above or below mean sea level
2. Pvt - Private use, not available to general public
3. A solid line box enclosed the airport name indicates FAR 93
Special Requirements - see Directory/Supplement
4. “NO SVFR” above the airport name indicates FAR 91 fixed-
wing special VFR flight is prohibited.
5. or following the airport identifier indicates Class C or
Class D Airspace
High Altitude - U.S.
6. Associated city names for public airports are shown above or
preceding the airport name. If airport name and city name are
the same, only the airport name is shown. The airport identifier in
parentheses follows the airport name. City names for military and
private airports are not shown.
7. Airport Ident ICAO Location Indicator shown outside contigu-
ous U.S.
8. AFIS Alaska only
High Altitude - Alaska
LIGHTING CAPABILITY
Lighting Available
Pilot Controlled Lighting
Part-time or on request
No lighting available
At private facilities- indicates no lighting
information is available
A symbol between the airport elevation and runway length means that runway lights are in operation sunset to sunrise.
A symbol indicates there is Pilot Controlled Lighting. A symbol means the lighting is part-time or on request, the
pilot should consult the Chart Supplement for light operating procedures. The Aeronautical Information Manual (AIM) thor-
oughly explains the types and uses of airport lighting aids.
VOR Minimum Operational Network (MON) Airports Designator
MON Airports with the Airport designator at the top of the Airport Data Block. The MON designation is to alert pilots
to those airports that have retained ILS and VOR instrument approach procedures for safe recovery in the event of a GPS
outage. Refer to the Aeronautical Information Manual (AIM) for expanded MON Airport guidance.
FAA Chart Users’ Guide - IFR Enroute Terms
RADIO AIDS TO NAVIGATION
All IFR radio NAVAIDs that have been flight checked and are operational are shown on all IFR Enroute Charts. Very High
Frequency/Ultrahigh Frequency (VHF/UHF) NAVAIDs, Very high frequency Omnidirectional Radio range (VORs), Tactical
Air Navigation (TACANs) are shown in black, and Low Frequency/Medium Frequency (LF/MF) NAVAIDs, (Compass Loca-
tors and Aeronautical or Marine NDBs) are shown in brown.
On IFR Enroute Charts, information about NAVAIDs is boxed as illustrated below. To avoid duplication of data, when two
or more NAVAIDs in a general area have the same name, the name is usually printed only once inside an identification
box with the frequencies, TACAN channel numbers, identification letters, or Morse Code Identifications of the different
NAVAIDs are shown in appropriate colors.
NAVAIDs in a shutdown status have the frequency and channel number crosshatched. Use of the NAVAID status "shut-
down" is only used when a facility has been decommissioned but cannot be published as such because of pending
airspace actions.
NAVIGATION AND COMMUNICATION BOXES - COMMON ELEMENTS
LOW ENROUTE CHARTS
RCO Frequencies
NAVAID Name, SSV(s)
FREQ, Ident, CH, Morse Code
Latitude, Longitude
Controlling FSS Name
HIGH ENROUTE CHARTS
RCO Frequencies
NAVAID Name
Frequency, Ident, SSV(s), Channel
Latitude, Longitude
Controlling FSS Name
COMMON ELEMENTS (HIGH AND LOW CHARTS)
RCO FREQUENCY
Single Frequency
Multiple Frequencies
Frequencies transmit and receive except those followed by R and
T:
R - Receive Only T - Transmit Only
NAVAID BOX
Thin line NAVAID boxes without frequency(s) and FSS radio name
indicates no FSS frequencies available.
Shadow NAVAID box indicates NAVAID and Flight Service Station
(FSS) have same name.
VHF/UHF LF/MF
FAA Chart Users’ Guide - IFR Enroute Terms
NAVAID STANDARD SERVICE VOLUME (SSV) CLASSIFICATIONS
SSV Class Altitudes Distance (NM)
(T) Terminal 1000’ to 12,000’ 25
(L) Low Altitude 1000’ to 18,000’ 40
(H) High Altitude 1000’ to 14,500’
14,500’ to 18,000’
18,000’ to 45,000’
45,000’ to 60,000’
(VL) VOR Low 1000’ to 5,000’
5,000’ to 18,000’
(VH) VOR High 1000’ to 5,000’
5,000’ to 14,500’
14,500’ to 18,000’
18,000’ to 45,000’
45,000’ to 60,000’
(DL) DME Low & (DH) DME High* 1000’ to 12,900’ 40 increasing to 130
(DL) DME Low 12,900’ to 18,000’ 130
(DH) DME High 12,900’ to 45,000’
45,000’ to 60,000’
* Between 1000’ to 12,900’, DME service volume follows a parabolic curve used by flight managment computers.
Notes: For NAVAIDs with two SSVs, the SSV for each component is shown in paired parentheses with the VOR SSV
shown first followed by the DME or TACAN SSV. Additionally, High Altitude facilities provide Low Altitude and Terminal
service volume and Low Altitude facilities provide Terminal service volume. Altitudes are with respect to the station’s
site elevation. Coverage is not available in a cone of airspace directly above the facility. In some cases local conditions
(terrain, buildings, trees, etc.) may require that the service volume be restricted. The public shall be informed of any
such restriction by a remark in the NAVAID entry or by a NOTAM.
DISTANCE MEASURING EQUIPMENT
Facilities that operate in the “Y” mode for DME reception (Y)
VOICE COMMUNICATIONS VIA NAVAID
Voice Transmitted
No Voice Transmitted
NAVAID SHUTDOWN STATUS VHF/UHF LF/MF
PART TIME OR ON-REQUEST VHF/UHF LF/MF
AUTOMATED WEATHER BROADCAST SERVICES
ASOS/AWOS - Automated Surface Observing Station/Automated
Weather Observing Station
VHF/UHF LF/MF
Automated weather, when available, is broadcast on the associ-
ated NAVAID frequency.
LATITUDE AND LONGITUDE
Latitude and Longitude coordinates are provided for those
NAVAIDs that make up part of a route/airway or a holding pattern.
All TACAN facilities will include geographic coordinates.
LOW ENROUTE HIGH ENROUTE
FAA Chart Users’ Guide - IFR Enroute Terms
AIRSPACE INFORMATION
CONTROLLED AIRSPACE
Controlled airspace consists of those areas where some or all aircraft are subjected to air traffic control within the follow-
ing airspace classifications of A, B, C, D, & E.
Air Route Traffic Control Centers (ARTCC) are established to provide Air Traffic Control to aircraft operating on IFR flight
plans within controlled airspace, particularly during the enroute phase of flight. Boundaries of the ARTCCs are shown in
their entirety using the symbol below.
ARTCC Name
Site Name
Frequency
Air Route Traffic Control Center (ARTCC)
When Controller Pilot Data Link Communication (CPDLC) exists for an ARTCC, the text CPDLC (LOGON KUSA) will be
shown parallel to the boundary above or below the ARTCC identification as shown below.
Air Route Traffic Control Center (ARTCC) with
Controller Pilot Data Link Communication (CPDLC)
The responsible ARTCC Center names are shown adjacent and parallel to the boundary line. ARTCC sector frequencies
are shown in boxes outlined by the same symbol.
ARTCC Name
Site Name
Frequency
ARTCC Remoted Sites with
discrete VHF and UHF frequencies
Class A Airspace is depicted as open area (white) on the IFR Enroute High Altitude Charts. It consists of
airspace from 18,000 Mean Sea Level (MSL) to FL600.
Class B Airspace is depicted as screened blue area with a solid line encompassing the area.
Class C Airspace is depicted as screened blue area with a dashed line encompassing the area with a let-
ter “C” enclosed in a box following the airport name.
Class B and Class C Airspace consist of controlled airspace extending upward from the surface or a des-
ignated floor to specified altitudes, within which all aircraft and pilots are subject to the operating rules and
requirements specified in the Federal Aviation Regulations (UHF) 71. Class B and C Airspace are shown
in abbreviated forms on IFR Enroute Low Altitude Charts. A general note adjacent to Class B airspace
refers the user to the appropriate VFR Terminal Area Chart.
Class D Airspace (airports with an operating control tower) are depicted as open area (white) with a letter
“D” enclosed in a box following the airport name.
Class E Airspace is depicted as open area (white) on the IFR Enroute Low Altitude Charts. It consists of
airspace below FL180.
UNCONTROLLED AIRSPACE
Class G Airspace within the United States extends to 14,500’ MSL. This uncontrolled airspace is shown
as screened brown.
SPECIAL USE AIRSPACE
Special Use Airspace (SUA) confines certain flight activities, restricts entry, or cautions other aircraft operating within
specific boundaries. SUA areas are shown in their entirety, even when they overlap, adjoin, or when an area is designated
within another area. SUA with altitudes from the surface and above are shown on the IFR Enroute Low Altitude Charts.
Similarly, SUA that extends above 18,000' MSL are shown on IFR Enroute High Altitude Charts. IFR Enroute Charts
tabulations identify the type of SUA, ID, effective altitudes, times of use, controlling agency and the panel it is located on.
FAA Chart Users’ Guide - IFR Enroute Terms
Users need to be aware that a NOTAM addressing activation will NOT be issued to announce permanently listed times of
use.
High and Low Low Altitude Only
P - Prohibited Area MOA - Military Operations Area
R - Restricted Area A - Alert Area *
W - Warning Area
* Alert Areas do not extend into Class A, B, C and D airspace, or Class E airport surface areas.
See Airspace Tabulation on chart for complete information.
OTHER AIRSPACE
FAR 91 Special Air Traffic Rules are shown with the type NO SVFR above the airport name.
FAR 93 Special Airspace Traffic Rules are shown with a solid line box around the airport name, indicating FAR 93 Spe-
cial Requirements see Chart Supplement.
Mode C Required Airspace (from the surface to 10,000' MSL) within 30 NM radius of the primary airport(s) for which a
Class B airspace is designated, is depicted on IFR Enroute Low Altitude Charts as a blue circle labeled MODE C & ADS-B
OUT 30 NM.
MODE C & ADS-B OUT
30 NM
Mode C & ADS-B Out is also required for operations within and above all Class C airspace up to 10,000' MSL, but not
depicted. See FAR 91.215 and the AIM.
INSTRUMENT AIRWAYS
The FAA has established two fixed route systems for air navigation. The VOR and LF/MF system-designated from 1,200'
Above Ground Level (AGL) to but not including FL 180 is shown on IFR Enroute Low Altitude Charts, and the Jet Route
system designated from FL 180 to FL 450 inclusive is shown on IFR Enroute High Altitude Charts.
VOR LF/MF AIRWAY SYSTEM (IFR LOW ALTITUDE ENROUTE CHARTS)
In this system VOR airways - airways based on VOR or VORTAC NAVAIDs - are depicted in black and identified by a "V"
(Victor) followed by the route number (e.g., "V12").
LF/MF airways - airways based on LF/MF NAVAIDs - are sometimes called "colored airways" because they are identified
by color name and number (e.g., "Amber One", charted as "A1"). In Alaska, Green and Red airways are plotted east and
FAA Chart Users’ Guide - IFR Enroute Terms
west, and Amber and Blue airways are plotted north and south. Regardless of their color identifier, LF/MF airways are
shown in brown.
AIRWAY/ROUTE DATA
On both series of IFR Enroute Charts, airway/route data such as the airway identifications, magnetic courses bearings or
radials, mileages, and altitudes (e.g., Minimum Enroute Altitudes (MEAs), Minimum Reception Altitudes (MRAs), Maxi-
mum Authorized Altitudes (MAAs), Minimum Obstacle Clearance Altitudes (MOCAs), Minimum Turning Altitudes (MTAs)
and Minimum Crossing Altitudes (MCAs)) are shown aligned with the airway.
As a rule the airway/route data is charted and in the same color as the airway, with one exception. Charted in blue, Global
Navigation Satellite System (GNSS) MEAs, identified with a "G" suffix, have been added to "V" and "colored airways" for
aircraft flying those airways using Global Positioning System (GPS) navigation.
Airways/Routes predicated on VOR or VORTAC NAVAIDs are defined by the outbound radial from the NAVAID. Airways/
Routes predicated on LF/MF NAVAIDs are defined by the inbound bearing.
• Minimum Enroute Altitude (MEA) - The MEA is the lowest published altitude between radio fixes that assures
acceptable navigational signal coverage and meets obstacle clearance requirements between those fixes. The
MEA prescribed for a Federal airway or segment, RNAV low or high route, or other direct route applies to the en-
tire width of the airway, segment, or route between the radio fixes defining the airway, segment, or route. MEAs for
routes wholly contained within controlled airspace normally provide a buffer above the floor of controlled airspace
consisting of at least 300 feet within transition areas and 500 feet within control areas. MEAs are established
based upon obstacle clearance over terrain and man-made objects, adequacy of navigation facility performance,
and communications requirements.
• Minimum Reception Altitude (MRA) - MRAs are determined by FAA flight inspection traversing an entire route
of flight to establish the minimum altitude the navigation signal can be received for the route and for off-course
NAVAID facilities that determine a fix. When the MRA at the fix is higher than the MEA, an MRA is established for
the fix and is the lowest altitude at which an intersection can be determined.
• Maximum Authorized Altitude (MAA) - An MAA is a published altitude representing the maximum usable
altitude or flight level for an airspace structure or route segment. It is the highest altitude on a Federal airway, jet
route, RNAV low or high route, or other direct route for which an MEA is designated at which adequate reception
of navigation signals is assured.
• Minimum Obstruction Clearance Altitude (MOCA) - The MOCA is the lowest published altitude in effect be-
tween radio fixes on VOR airways, off-airway routes, or route segments that meets obstacle clearance require-
ments for the entire route segment and assures acceptable navigational signal coverage only within 25 statute (22
nautical) miles of a VOR. A MOCA is only shown on the Enroute Low Charts and only published when it is lower
than the MEA. When shown, it is preceded by an asterisk.
• Minimum Turning Altitude (MTA) - Minimum turning altitude (MTA) is a charted altitude providing vertical and
lateral obstruction clearance based on turn criteria over certain fixes, NAVAIDs, waypoints, and on charted route
segments. When a VHF airway or route terminates at a NAVAID or fix, the primary area extends beyond that
termination point. When a change of course on VHF airways and routes is necessary, the enroute obstacle clear-
ance turning area extends the primary and secondary obstacle clearance areas to accommodate the turn radius
of the aircraft. Since turns at or after fix passage may exceed airway and route boundaries, pilots are expected to
adhere to airway and route protected airspace by leading turns early before a fix. The turn area provides obstacle
clearance for both turn anticipation (turning prior to the fix) and flyover protection (turning after crossing the fix).
Turning fixes requiring a higher MTA are charted with a flag along with accompanying text describing the MTA
restriction.
FAA Chart Users’ Guide - IFR Enroute Terms
• Minimum Crossing Altitude (MCA) - An MCA is the lowest altitude at certain fixes at which the aircraft must
cross when proceeding in the direction of a higher minimum enroute IFR altitude. MCAs are established in all
cases where obstacles intervene to prevent pilots from maintaining obstacle clearance during a normal climb to a
higher MEA after passing a point beyond which the higher MEA applies. The same protected enroute area vertical
obstacle clearance requirements for the primary and secondary areas are considered in the determination of the
MCA.
Victor Route (with RNAV/GPS MEA shown in blue)
AREA NAVIGATION (RNAV) "T" ROUTE SYSTEM
The FAA has created new low altitude area navigation (RNAV) "T" routes for the enroute and terminal environments. The
RNAV routes will provide more direct routing for IFR aircraft and enhance the safety and efficiency of the National Air-
space System. To utilize these routes aircraft are required to be equipped with IFR approved GNSS. In Alaska, TSO-145a
and 146a equipment is required.
Low altitude RNAV only routes are identified by the prefix "T", and the prefix "TK" for RNAV helicopter routes followed by a
three digit number (T-200 to T-500). Routes are depicted in blue on the IFR Enroute Low Altitude Charts. RNAV route data
(route line, identification boxes, mileages, waypoints, waypoint names, magnetic reference courses and MEAs) will also
be printed in blue. Magnetic reference courses will be shown originating from a waypoint, fix/reporting point or NAVAID.
GNSS MEA for each segment is established to ensure obstacle clearance and communications reception. GNSS MEAs
are identified with a "G" suffix.
Joint Victor/RNAV routes are charted as outlined above except as noted. The joint Victor route and the RNAV route iden-
tification boxes are shown adjacent to each other. Magnetic reference courses are not shown. MEAs are charted above
the appropriate identification box or stacked in pairs, GNSS and Victor. On joint routes, RNAV specific information will be
printed in blue.
UNUSABLE AIRWAY/ROUTE SEGMENTS
Airway/Route segments designated by the FAA as unusable will be depicted as shown below.
Unusable Victor Route
FAA Chart Users’ Guide - IFR Enroute Terms
Pilots should not file a flight plan for or accept a clearance that includes navigation on any route or route segment depict-
ed as unusable. Pilots using RNAV may request ATC clearance to fly point-to-point between valid waypoints or fixes, even
those on routes depicted as unusable (refer to AC 90-108 for RNAV eligibility).
Coincident Airways/Routes with Unusable Segment
When two airways/routes are coincident, but only one airway/route is designated as unusable, the following note indicat-
ing which airway the unusable symbology applies to will be placed in close proximity to the airway/route identifiers.
OFF ROUTE OBSTRUCTION CLEARANCE ALTITUDE (OROCA)
The Off Route Obstruction Clearance Altitude (OROCA) is depicted on IFR Enroute Low Altitude and Pacific charts and
is represented in thousands and hundreds of feet above MSL. OROCAs are shown in every 30 x 30 minute quadrant on
Area Charts, every one degree by one degree quadrant for IFR Enroute Low Altitude Charts - U.S. and every two de¬gree
by two degree quadrant on IFR Enroute Low Altitude Charts - Alaska. The OROCA is based on the highest known terrain
feature or obstruction in each quadrangle, bounded by the ticked lines of latitude/longitude including data 4 NM outside
the quadrant. In this example the OROCA represents 12,500 feet.
OROCA is computed just as the Maximum Elevation Figure (MEF) found on Visual Flight Rule (VFR) Charts except that it
provides an additional vertical buffer of 1,000 feet in designated non-mountainous areas and a 2,000 foot vertical buffer in
designated mountainous areas within the United States. Evaluating the area around the quadrant provides the chart user
the same lateral clearance an airway provides should the line of intended flight follow a ticked line of latitude or longitude.
OROCA altitudes are not assessed for NAVAID signal coverage, air traffic control surveillance, or communications cover-
age, and are published for general situational awareness, flight planning, and in-flight contingency use. OROCAs can be
found over all land masses and open water areas containing man-made obstructions (such as oil rigs).
MILITARY TRAINING ROUTES (MTRs)
Military Training Routes (MTRs) are routes established for the conduct of low-altitude, high-speed military flight training
(generally below 10,000 feet MSL at airspeeds in excess of 250 knots Indicated Air Speed). These routes are depicted in
brown on IFR Enroute Low Altitude Charts, and are not shown on inset charts or on IFR Enroute High Altitude Charts. IFR
Enroute Low Altitude Charts depict all IFR Military Training Routes (IRs) and VFR Military Training Routes (VRs), except
those VRs that are entirely at or below 1,500 feet AGL.
MTRs are identified by designators (IR-107, VR-134) that are shown in brown on the route centerline. Arrows are shown
to indicate the direction of flight along the route. The width of the route determines the width of the line that is plotted on
the chart:
Route segments with a width of 5 NM or less, both sides of the centerline, are shown by a .02" line.
Route segments with a width greater than 5 NM, either or both sides of the centerline, are shown by a .035" line.
MTRs for particular chart pairs (ex. L1/2, etc.) are alphabetically, then numerically tabulated. The tabulation includes MTR
type and unique identification and altitude range.