At approximately 11:30 a.m. on May 15, 1918, the U.S. Post Office inaugurated regular airmail service, using Curtiss JN-4H biplanes to fly between Washington, D.C. and New York City, with a stop in Philadelphia. It took two more years of dogged effort and experimentation, marred by dozens of crashes and 16 fatalities, for the service to fly the mail all the way across the country.

By 1927, the Post Office had nursed the airmail service through its infancy and was ready to hand it off to private companies, like Boeing Air Transport and National Air Transport, which eventually developed into United Airlines. With aircraft like the Boeing 40C and Stearman Speedmail, and with pilots like Charles Lindbergh, contract mail carriers laid the foundation for the most expansive national air transportation system in the world.​

As the U.S. Postal Service celebrates the centennial with a new Forever stamp, we dug into our archive to showcase stories on the dramatic early days of airmail service, which transformed aviation almost as much as it did communications.

Photo: Loading mail sacks onto an airplane near Omaha, Nebraska, in the mid-1920s. (Smithsonian Institution)