On December 10, 1919, appearing before the U.S. House Committee on Post Offices and Post Roads, Second Assistant Postmaster General Otto Praeger requested $3 million for the creation and operation of airmail routes between New York – San Francisco, Pittsburgh – Milwaukee, New York – Atlanta, and St. Louis – Minneapolis. He argued that these routes would further the ultimate goal of the Air Mail Service, which he stated again, was "to develop aviation to that point where corporations will come in and run the lines. Then we will make contracts with them as we do with power boat or steamship lines." In agreement with the purpose of the service, but unimpressed with the breadth of the growth, Congress allotted Praeger $1,375,000 and told him to concentrate on the transcontinental New York – San Francisco route.
In a characteristic burst of confidence, Praeger put aside his disappointment and fixed September 1, 1920 as the opening date of the first transcontinental service. The route would keep the New York – Chicago portion that was already in operation, although some field changes were made. Earlier that year the service had moved the airmail field in Chicago from Grant Park to Checkerboard Field in the Chicago suburb of Maywood. The airmail field located at Woodland Hills Park in Cleveland was resituated to the more useful Glenn Martin Field.
From Chicago, the transcontinental route was fixed through Iowa City, Iowa, Omaha and North Platte in Nebraska, Cheyenne, Rawlins and Rock Springs in Wyoming, Salt Lake City, Utah, Elko and Reno, Nevada, ending in San Francisco, California.
Between the main and refueling stops officials established a series of emergency landing fields. Most were on farms or privately owned lands. Each owner received a subsidy from the postal service to keep some land clear as an emergency landing strip. Of course, not all owners kept the fields as clear as the pilots would like and occasionally landing on an emergency landing strip was as tricky as landing in a grain field.
On May 15, 1920, the Chicago – Omaha section of the route was opened, even as postal officials scrambled to ensure that each segment of the route was fully stocked and had plenty of airplanes available. There were several setbacks with the aircraft Praeger planned to use on the transcontinental route. By August 1920, the service was forced to give up on its experimental use of twin-engine de Havilland machines and the first day of service was rescheduled for September. However, trouble with the Junkers-Larsen JL-6 airplane forced Praeger to postpone one more week.
On September 3, 1920, tragedy struck when the first pilot hired by the postal service, Max Miller, was killed in a fiery crash of a Junkers-Larsen JL-6 aircraft near Morristown, New Jersey. Mechanic Gustav Rierson, who was traveling with Miller in the airplane, saved some of the mail load by throwing the bags overboard as the airplane burned. Both men were killed, and their bodies burned beyond recognition in the ensuing crash. Miller was one of the service's best known and most popular pilots. His death brought media and public scrutiny to the service just as it was about to launch its transcontinental triumph. Reporting Miller's death that day, the New York Sun blamed the crash on the postal officials, saying that "[Postmaster General] Burleson's most spectacular fad continues to be indulged in at ghastly expense."
The Junkers were eventually junked, and the old reliable ex-army de Havilland aircraft became the mail airplanes used on the new transcontinental route. The route finally opened on September 8, 1920, when pilot Randolph Page flew out of from Hazelhurst Field, New York. The mail was transferred through pilot and aircraft relays until it was flown into San Francisco's Marino Field by pilot Edison Mouton who arrived there September 11, 1920 at 2:33 p.m. Praeger had promised a transcontinental service that would take a mere 54 hours. Working at their fastest, pilots and airplanes made the trip in 83 hours. Nevertheless, the idea of coast-to-coast airmail delivery sparked the public imagination, and the trips were considered a great success.