Douglas C-54 Skymaster

The Douglas C-54 Skymaster was the military version of the DC-4 airliner, and was the first truly effective four-engined transport aircraft to enter USAAF service.
The Douglas R5D was the US Navy’s version of the C-54 Skymaster, the military version of the DC-4 airliner.
The Douglas R3D was the Navy’s version of the commercially unsuccessful DC-5 short haul passenger transport.
The Douglas C-110 was the designation given to three DC-5 airliners after they were impressed into USAAF service during 1944.
The designation Douglas XC-112 was given to two different aircraft, one a proposed pressurized version of the C-54 and the other the first military DC-6.
The Douglas XC-114 was a lengthened and re-engined version of the C-54 Skymaster.
The Douglas XC-115 was to have been a version of the XC-114 powered by four 1,650 Packard V-1650-209 engines.
The single Douglas XC-116 was a sister to the XC-114, and like that aircraft was a version of the C-54 with a longer (100ft 7in compared to 93ft 10in) fuselage.