In February 1936, Douglas began the design of a large four-engine commercial transport that would be capable of carrying twice as many passengers as the DC-3 over distances of 2200 miles.
The result: The Douglas DC-4 / C-54 Skymaster.
On February 14, 1942, the first DC-4, designated a C-54 Skymaster for the military, took flight and started the age of the four-engine transports. The production line closed in 1947, but many of the military variants found use in civil service.
A total of 1.245 were produced.