Douglas DC-4 DC-4E

The DC-4 name had already been used for a four-engined 52-seat precursor that first flew in 1935 and never entered production; to tell it apart from the DC-4 proper it came to be known as the DC-4E. After United Airlines' proving flights it was obvious that the design was too inefficient and unreliable to operate economically, and the partner airlines — United, American Airlines, Eastern, Pan American and TWA — handed Douglas a lengthy list of changes.

Douglas folded those requirements into an entirely new, smaller design, the DC-4A: a simpler fuselage, Pratt & Whitney R-2000 Twin Wasp engines and a single fin and rudder instead of the DC-4E's tri-fin tail. Two features of the precursor were kept, and they would define the type: the tricycle landing gear and the unpressurised cabin. One example was built.