Originally Posted by Mainliner

United referred to itself from the late 1930’s to the mid 1960’s as the Main Line Airway (before United flew the friendly skies). The Main Line was United’s original route from New York to San Francisco, first known as U.S. Mail Route No. 1. It was formed by Boeing Air Transport and National Air Transport (both predecessor companies of United) in 1927. As noted by others on this thread, United used to refer to its aircraft as Mainliners, in the 1950’s through the early 1980’s United’s in-flight magazine was called “Mainliner”, and its advertising during this time often would refer to Mainliner Service.