Douglas mailplanes

The Douglas mailplanes were a family of 1920s American single-seat mail planes designed and built by the Douglas Aircraft Company and used on the main routes of the United States Air Mail service until three-engined aircraft arrived in 1928. In 1925 the Post Office asked Douglas for a replacement for its de Havilland DH.4 biplanes, and the company modified an O-2 observation biplane by covering the forward cockpit with a mail compartment and moving the pilot into the observer's seat, creating the M-1. Western Air Express ordered six M-2 aircraft, the Post Office ordered 50 M-3 aircraft, and a longer-winged M-4 followed, with one M-4A for Western Air Express. National Air Transport bought ten M-3s and eight M-4s at auction in 1926 and at one point flew 24 Douglas mailplanes, and most were scrapped after withdrawal.