Regional airliner were replaced by progressively longer-range designs. In the immediate post-war era these were typically Douglas DC-3s, although even the De Havilland Dragon Rapide biplane airliner remained in service for some time. This "hand-me-down" process of supplying aircraft continued with designs like the Convair 440, Douglas DC-6 and Vickers Viscount also serving in this role while the first jets were introduced. By the mid-1950s, demand for even more economical designs led to the production of the first custom feederliners. These were almost always turboprops, which had fuel economy on par with piston engine designs, but had far lower maintenance costs. Often
Airliner submissions they had made during the war for a "100 ton bomber". This evolved into the creation of the Bristol Brabazon. The Type II process was complicated by the proposition of Vickers that a move to the newly developed turboprop power should be made. The specification was, therefore ,split in two, with the conventional piston design going to the eventual de Havilland Dove and Airspeed Ambassador. The revolutionary VC.2 Viceroy, first flown in 1948, was the first turboprop design anywhere. The Type III requirement was developed as the Avro Tudor. The Type IV for the jet-powered aircraft went to de