I was perusing that perennial bestseller, the FAA’s “Aeronautical Information Manual,” the other night, and ran across an intriguing reference to code beacons and course lights. Code beacons, in general, flash identifying information in Morse code; coded course lights are used with rotating beacons of the Federal Airway System, are highly directional, and are paired back-to-back pointed along the airway. What interested me was the appended 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. (Aeronautical Information Manual, 2-2-2 Code Beacons and Course Lights)

Really? Some are still in service? I decided to investigate further.

As the Air Mail Service became better established in the 1920s and 30s, the Post Office and later the Aeronautics Branch of the U. S. Department of Commerce installed hundreds of lighted airway beacons across the country to facilitate night flying. They were spaced roughly ten miles apart; every third one had at least an emergency landing strip adjacent. Each tower carried a white rotating beacon with a 1,000W lamp and 24-inch diameter mirror, visible from all directions, plus the two course lights mentioned above. Airway beacons with a landing strip had green course markers, a detail reflected even today in the fact that the beacons for lighted land airports are green and white (seaplane airports are marked with yellow and white). Red course lights warned pilots that no safe haven would be found there. The beacons were numbered, and the last digit was coded by one of ten Morse code letters: W U V H R K D B G M, where W stood for “one”, U for “two”, and so on. Pilots memorized the phrase “When Undertaking Very Hard Routes, Keep Direction By Good Methods” to remember the order. By day, the locations could be identified by the number painted on the roof of the adjacent generator shed; a large concrete arrow set into the ground showed the direction to the next location. Remnants of these arrows are still found here and there, arousing curiosity among hikers and geocache hunters.

The first lighted airway beacon was installed in 1923; only five years later the earliest radio navigation aids began to spell the beacons’ obsolescence. Never hasty to abandon a proven system, the FAA did not decommission the last one until July 20, 1972, at Whitewater, California (near Palm Springs). The state of Montana, however, polled its pilot population and found that these aeronautical lighthouses were still valued as guides through the western mountains. Today, the Aeronautics Division of the Montana Department of Transportation maintains 16 beacons transferred from the Federal government – the only state to do so. The lights lead from Helena south to Monida Pass, north towards Great Falls, and west past Missoula to the Idaho state line. They bear romantic names like Mount Sentinel and Lookout Pass and are still shown on the Great Falls sectional chart.


Air Route Beacon in America by Air exhibition at the National Mall Building. 

The National Air and Space Museum received the last Federal airway beacon from the FAA in 1973, a year after it was taken out of service.  It stands in the America By Air gallery, rotating beacon flashing six times a minute, course lights patiently blinking long-long-short (“G”, meaning “nine”), as they have for over 70 years (see live web cam). The course lights are red, since there is no landing strip nearby, but the national aircraft collection has found a safe haven beside their beams nonetheless.

Related Topics Aviation Technology and Engineering Navigation
Twitter Comments? Contact Us
You may also like Twenty Years of GPS and Instrument Flight February 24, 2014