Trans World Airlines Douglas DC-4 The Douglas DC-4 is an American four-engined (piston), propeller-driven airliner developed by the Douglas Aircraft Company. Military versions of the plane, the C-54 and R5D, served during World War II, in the Berlin Airlift and into the 1960s. First flight 14 February 1942 Produced 1942 – August 1947 Primary users US Military United Airlines, American Airlines, Trans World Airlines, Buffalo Airways