The C-54 was the military derivative of the Douglas DC-4, a four-engine long range pressurized airliner with a three-man crew and accommodations for up to 49 passengers or 26 troops. Originally designed to a specification from United Airlines, the DC-4 had a maximum speed of 274 mph and a range of 3900 miles. The first 61 civilian orders were followed by a further buy for 71 from the USAAC though, in the end, most ended up in Army service.
To meet the military’s more stringent needs, the DC-4 was given a cargo door, stronger floor, cargo boom hoist and larger wing tanks. First flight of the military C-54 occurred on 26 March 1942. During the war years, 1242 C-54s were delivered with a wide variety of modifications. A few of the major ones were the C-54A, the original, fully militarized model capable of lifting 50 soldiers or 32,500 pounds of cargo; the JC-54D, which was modified for missile nose cone recovery; the C-54E, with larger Pratt & Whitney engines, bigger fuel tanks for longer range and a specially designed cabin for quick conversion between passenger and cargo roles; the C-54M, which was a C-54E stripped out to serve as a coal-carrier during the Berlin Airlift; the EC-54U, a post-war modification as an electronic counter-measures platform; and at least 14 sub-variants built for the US Navy originally called the R5D. There were numerous other variants which performed countless other roles, from VIP transport to multi-engine training.
Specifications:
Engines: Four 1,450-hp Pratt & Whitney R-2000-2SD-13G Twin Wasp radial piston engines.
Weight: Empty 43,300 lbs., Max Takeoff 73,000 lbs.
Wing Span: 117ft. 6in.
Length: 93ft. 10in.
Height: 27ft. 6in.
Performance:
Maximum Speed: 280 mph at 14,000 ft.
Ceiling: 22,300 ft.
Range: 2,500 miles
Armament: None
Number Built: 1000+ military versions
source=www.warbirdalley.com
As you can see, the C54 was used to transport supplies and troops. Not sure of the number of combat drops it was used for, but I will look. Pdog-0 fdiron-1