Douglas DC-4 C-54E

With the C-54E the last two cabin fuel tanks disappeared, moved into the wing. The space freed up became more freight or 44 passenger seats, and the version also gained provision for rapid conversion from passenger to cargo configuration, something military operations valued as much as civil ones later would.

125 were built. From them came the AC-54E airways calibration aircraft — EC-54E from 1962 — the SC-54E air-sea rescue conversions — HC-54E from 1962 — and the VC-54E staff transports. The Navy received 20 as the R5D-4, redesignated EC-54U in 1962. The C-54E airframe was also the basis of the XC-114, a single stretched example with Allison V-1710 engines.