In 1921, there were air routes linking some important cities in the United States, at the time, airplanes weren´t in condition of carring more than 16 passengers, and had to refuel more often than now, New York had 2 routes, one to Washington DC, which made a stop in Philadelphia to refuel and another to Chicago, with stops in Cleveland and Pittsburgh for being a longer distance, in the case of Chicago, there were 4 routes, one to New York that had the same stops in Cleveland and Pittsburgh, another to San Francisco that made 10 stops before arriving, being several of them: Cheyenne, Salt lake city and sacrament, another route was to St Louis, and the fourth one to Minneapolis.