Curtiss C-55

1941 military prototype of the Commando.

1 Commando converted by the USAAF as a military transport aircraft

The C-55 was effectively the initial prototype of the C-46. It was the military variant of the Curtiss-Wright CW-20T airliner which, as the world's largest twin-engined airplane, had attracted the interest of the USAAF. By the time the Air Force purchased the CW-20T prototype - now redesignated CW-20A internally by Curtiss - it had already ordered 200 production Commandos. The C-55 testing at Wright Field, OH was used to refine the design before the actual start of production. The main change introduced by the USAAF on the C-55 was the replacement of the underpowered 1,700-hp Wright R-2600-C14 engines by 1,850-hp Pratt & Whitney R-2800-5s.

The sole C-55 was eventually sold to BOAC in September 1941 to boost that airline's long-haul capacity and allow it to conduct transatlantic repatriation flights of US ferry pilots.