The FAA has established two fixed route systems
for air navigation. The VOR and LF/MF (low or
medium frequency) system—designated from 1,200'
AGL to but not including 18,000' MSL—is shown on
Low Altitude Enroute Charts, and the Jet Route system
—designated from 18,000' MSL to FL 450 inclusive
—is shown on High Altitude Enroute Charts.
VOR LF/MF AIRWAY SYSTEM
(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"). In Alaska and Canada, some segments of
low-altitude airways are based on LF/MF navaids and
are charted in brown instead of black.
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"). Green and Red
airways are plotted east and west, and Amber and
Blue airways are plotted north and south. Regardless
of their color identifier, LF/MF airways are shown in
brown. U.S. colored airways exist only in Alaska, those
within the conterminous U.S. have been rescinded.
On both series of Enroute Charts, airway/route
data such as the airway identifications, bearings or radials,
mileages, and altitude (e.g., MEA, MOCA, MAA)
are shown aligned with the airway and in the same
color as the airway.
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.
AREA NAVIGATION (RNAV) "T" ROUTE SYSTEM
The FAA has created new low altitude area
navigation (RNAV) routes for the en route and terminal
environments. The RNAV routes will provide more direct
routing for IFR aircraft and enhance the safety and
efficiency of the National Airspace System. To utilize
these routes aircraft will need to be equipped with IFR
approved Global Navigation Satellite System (GNSS).
In Alaska, TSO-145a and 146a equipment is required.
Low altitude RNAV only routes are identified by the letter
"T" prefix, followed by a three digit number (T-200
to T-500). Routes are depicted in aeronautical blue on
the IFR Enroute Low Altitude charts. RNAV route data
(route line, identification boxes, mileages, waypoints,
waypoint names, magnetic reference bearings, and
MEAs) will also be printed in aeronautical blue. Magnetic
reference bearings will be shown originating from
a waypoint, fix/reporting point or NAVAID. A GNSS
minimum IFR en route altitude (MEA) for each segment
will be established to ensure obstacle clearance
and communications reception. MEAs will be identi-
fied with a "G" suffix.