Douglas DC-4 C-54D

The C-54D is the Skymaster's most common variant: a C-54B with more powerful R-2000-11 engines, which entered service in August 1944. 380 were built, almost a third of the 1,163 military C-54s produced between 1942 and January 1946.

Its abundance explains the long list of conversions carrying its letter: the AC-54D with special electronic calibration and communications equipment — redesignated EC-54D — the 38 Convair-converted SC-54D search and rescue aircraft later called HC-54D Rescuemaster, the nine JC-54D temporarily adapted for missile tracking and nose-cone recovery, the TC-54D multi-engine trainers, the VC-54D VIP transports and the WC-54D weather reconnaissance aircraft. The Royal Air Force received 22 C-54Ds as the Skymaster I, and the US Navy took 95 as the R5D-3.