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. So in the 1920s, the US Post Office began experimenting with this new flying machine that was recently used with great success in the First World War. 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. Bad weather, poor instruments, old aircrafts and maintenance errors were among the many threats pilots had to deal with when flying a mission. This was also the time when there were no GPS, radar or radio guidance. Pilots had to navigate their way across the country by picking out visible landmarks up from the air. This made flying at night impossible. Even during the day, not all regions were recognizable, especially when flying above vast stretches of empty, repetitive deserts.

Remnants of a Transcontinental Air Mail Route Beacon atop a bluff in St. George, Utah. Photo credit: Dppowell/Wikimedia