Definition
A Federal airway based on Low/Medium Frequency non-directional radio beacons (NDBs), operating in the 190 to 535 kHz frequency band. L/MF airways are designated by color names (Green, Red, Amber, Blue) followed by a number, and exist primarily in coastal Alaska and a few other remote areas where VOR coverage is limited or impractical.
Plain English
An older type of published airway that uses ground-based beacons broadcasting on low or medium radio frequencies, rather than the more common VOR stations. You'll mostly find these in remote areas like coastal Alaska.
Context Anchor
Seen in instrument flying material, enroute chart discussions, and FAA descriptions of the airway and route system.
Derivation
L/MF stands for Low/Medium Frequency, referring to the radio frequency bands these airways rely on. The term 'airway' simply means a published, protected route through the sky — a highway in the air.
Why Pilots Care
Provides a usable navigation path when VOR or GPS routing is unavailable or unreliable.
Intuition Check
Do not read airway as a physical lane in the sky. Here it means a published navigation route defined by radio signals and shown in aviation procedures or charts.
Example Sentence 1
Flying IFR along the Alaskan coast, the pilot filed a route that included an L/MF airway because no VOR coverage was available in that area.
Example Sentence 2
ATC cleared the flight direct via the amber L/MF airway after the VOR went out of service.