If you ever found yourself traveling in U.S., look around – in some places you may find large concrete arrows on the ground. Interestingly, not even all locals know what they are for. There are some conspiracy theories saying that these arrows are a part of a big military network, but reality is a bit different. So what are they for?
Actually, these arrows are remnants of The Transcontinental Airway System – a navigational aid deployed in the United States during the 1920s. The system was proposed by National Advisory Committee for Aeronautics, funded by the United States Congress, deployed by the Department of Commerce and managed by the Bureau of Standards Aeronautical Branch – this was a huge government effort aimed to improving the infrastructure of air travel.
The problem was that flying at night was both scary and dangerous. At that time satellite navigation was not a thing at all and airplanes were not great either. The danger of ramming straight into a mountain range was very real, but even getting lost could have cost a lot of money or even lives of the crew. This is why night time flights were pretty much non-existent. New lighted Airway Beacons were supposed to solve this issue, even though their effectiveness was often limited by weather conditions and visibility.
610 mm diameter Airway Beacons were mounted on 16 m high towers every 10 miles or so in major airways. Each beacon was flashing its identification numbers in Morse code. Pilots were supposed to look at each tower and confirm their location and heading. This allowed for a relatively accurate navigation before radio navigation was even a thing.
Beacon towers had a pretty simple angle iron construction. They were built on concrete footings, which, as you might have guessed by now, were shaped as giant arrows, pointing towards the next beacon. Transcontinental Airway System totalled 1500 beacons in 1933, but at that time the system pretty much reached its full capacity.
Radio navigation pretty much rendered flawed beacon system out-dated. Most towers were removed and went straight into junk yards. However, these concrete arrows were too difficult to remove. And what for? They don’t really bother anyone. At least not now – during the Second World War some of them were destroyed in order to prevent the possibility that enemy air forces could use those arrows for navigation.
And that is what those concrete arrows are – just remnants of the aircraft navigation system of the past. However, not all beacon towers were removed – 19 updated beacons still remain in service in Montana. In mountainous terrain these beacons still serve as a visual aid, especially for smaller airplanes.