In 1938, the Douglas Aircraft Co. decided to produce a four-engine transport about twice the size of the DC-3. It developed the single DC-4E to carry 42 passengers by day or 30 by night. The DC-4E had complete sleeping accommodations, including a private bridal room.

It proved too expensive to maintain, so airlines agreed to suspend development in favor of the less complex DC-4, which was not put into commercial service until 1946. Its military derivative was the C-54 ”Skymaster” transport, ordered by the U.S. Army Air Forces in 1942.

After World War II, commercial airlines placed more than 300 civilian DC-4 transports into service, these DC-4s, along with C-54s converted for civil use, carried more passengers than any other four-engine transport.