In the early 1900s, the fastest way to deliver mail was by rail, but there was a machine that could travel faster than trains, and that was, of course, the airplane. There was, however, one major problem: unlike trains that could run all night and on all weather, airplanes could only fly during the day and only when the weather permits.
Flying was still a risky business. This was also the time when there were no GPS, radar or radio guidance. The Post Office came up with a solution - giant, concrete arrows laid on the ground that literally pointed the right direction to the airmail pilots.