The designation DC-4 was used by Douglas Aircraft Company when developing the DC-4E as a large, four-engined type to complement its very successful DC-3, already in widespread operation. The DC-4 was intended to fulfil United Airlines' requirement for a long-range passenger airliner. The DC-4E (E stands for experimental) emerged as a 52-passenger airliner with a fuselage of unusually wide cross-section for its day and a triple fin tail unit, similar to that later used by Lockheed on its Constellation.
