In June 1938 Douglas flew the prototype of an advanced four engine airliner with tricycle landing gear and pressurized accommodation. This DC-4E was in reality too advanced for its period and, suffering many problems with several of its systems, was cancelled. The same basic concept was then used for the DC-4 of 1939, which was unpressurized and featured simplified systems. The US became embroiled in the Second World War before the new DC-4 could fly, and the type was then adapted with little difficulty as the c-54 Skymaster to meet a US Army Air Forces requirement for a trans oceanic transport. The type first flew in February 1942. Production for the military eventually totaled 1,122 aircraft that served with little glamour but great distinction.

Description	Specifications
Manufacturer: Douglas	Length: 93 ft. 10 in.
First Flight:	Height: 27 ft. 6 in.
Model: A	Wing Span: 117 ft. 6 in.
Crew: Six	Wing Area: 1,460.0 sq. ft.
Nickname: Skymaster	Empty Weight: 37,000 lb.
Basic Role: Long range transport.	Max. Weight: 62,000 lb.
Other Versions: C-54 militarized DC-4A airliners. C-54A variant with different engines and usable in the convertible passenger or freight role thanks to its reinforced floor and cargo doors. C-54B heavier C-54A with provision for litters. C-54C VIP transport. C-54D re engine C-54B. C-54E long range version. C-54G high density passenger transport. R-4D-1/4 US Navy equivalents of the C-54, A, D, and G Skymaster Mk I British equivalent of C-54B and D	Payload: Fifty passengers or freight.
Principal User: Great Britain, and USA.	Propulsion
Performance	Power Plant: Pratt & Whitney R-2000-7 radial piston engines.
Range: 3,900 miles.	Horsepower: 1,290-hp.
Max. Speed: 275 mph at optimum altitude.	No. Of Engines: Four
Ceiling: 22,000 ft.
Climb Rate: 10,000 ft. in 14 minutes 48 seconds.