Definition
Green 13 is the designator for a specific colored federal airway, part of the older color-coded low-altitude airway system used in the United States, primarily in coastal and offshore regions of Alaska. Colored airways (Green, Red, Amber, Blue) run generally east-west (Green and Red) or north-south (Amber and Blue) and are based on non-directional beacons (NDBs) rather than VORs.
Plain English
Green 13 is the name of one particular published low-altitude air route. It belongs to an older system of airways that are named by color and number instead of by the letter V used for most U.S. airways today. These color-named routes still exist mainly in parts of Alaska and run roughly east-west.
Context Anchor
Seen on IFR en route charts and in FAA discussions of the airway and route system, especially where colored airways are described.
Derivation
The color-coded naming system dates from early U.S. airway development, when airways were marked by colored lights and beacons. Green and Red were assigned to east-west routes; Amber and Blue to north-south routes. The name 'Green 13' simply identifies the 13th airway in the Green (east-west) series.
Why Pilots Care
Allows pilots to follow a pre-established, protected route between navigation aids while remaining in controlled airspace.
Intuition Check
Green does not mean the route is simply marked as safe or that every chart will draw it in green. Here, Green is part of the airway’s official name, and 13 identifies the specific route.
Example Sentence 1
The clearance routed the flight along Green 13 from Anchorage to a fix on the coast.
Example Sentence 2
ATC cleared the aircraft direct to join Green 13 at the appropriate altitude.