Prying funds out of a stingy U.S. Congress for air mail service proved to be a difficult matter, and it was not until 1916 that Congress appropriated funds for air mail contracts. No businesses were found that were willing to sink money into buying aircraft for such a risky venture, consequently no contracts were ever let. Finally, in 1918, Congress gave the Postal Service $100,000 to establish its own air mail routes. The Army provided the pilots and airplanes for the first three months of the Postal Service air mail program. The mail was delivered in a timely manner but it was not a financial success.

The first leg of trans-continental mail service was between Cleveland and Chicago and did not occur until 1919. By 1920, air mail service had finally begin to develop. Within two years, the growing air mail service connected cities along the Atlantic Seaboard with Pittsburgh, Cleveland, and Chicago, developing a fairly efficient air mail system in the eastern U.S. The first transcontinental air mail service between San Francisco and New York was in 1921.

Flying the mail was very risky business, and was not for the faint hearted. Air mail pilots had a tough time, and it took a really hardy soul to be an air mail pilot. Sitting in cold, frail, open cockpit airplanes, bundled up in many layers of warm clothing, these hardy adventurers faced very difficult weather conditions. They flew in high, erratic winds, subzero temperatures, fog, rain, sleet, and snow. In the west, they flew not only over very rugged terrain, but also through dangerous narrow mountain passes, as airplanes at the time could not get the altitude needed to fly over the high mountains. The average life expectancy of the air mail pilot was three years.

These daring pilots had no charts, only road maps provide by the Post Office which showed only towns that had post offices. Radios were rare, and the only navigational aids were a compass and an altimeter. As one pilot put it, "the instruments just got in his way as he looked over the side of the plane." They flew the mail in the same manner that the Pony Express delivered the mail half a century earlier. Each pilot had his own route. He would fly to the town where he was to meet the pilot of the next section. They would trade mail, than make the return trip. The pilots flew by following landmarks they memorized, very often following railroads. This meant they could only fly in daylight. When it got dark they would land, and put the mail on the first train that was going in the direction the mail needed to go. It was an improvement over land delivered mail but it still was not a very efficient way to deliver the mail.

By the mid-1920s, with improved weather reporting, the addition of some navigational aids, better and more reliable communications, and enclosed aircraft which could fly higher, mail service began to change. The emphasis was now on safety and reliability, as well as expansion of mail service. It was clear by this time that air mail service would not be at its best until the pilots could fly at night. To solve this problem the government instituted a light system for pilots to navigate by at night, called the Airway Beacon System.