Power would be provided by two Pratt & Whitney R-4360 Wasp Major radial engines each driving a set of pusher contra-rotating propellers.

[2] Based on studies of heavy, long-range fighters that had been undertaken prior to the American involvement in World War II, the United States Army Air Forces initially ordered two prototypes in November 1941.

[3] The major role for the proposed aircraft was to act as an "escort" fighter to protect heavy bombers that would have to operate over occupied Europe even if Britain was conquered.

[3] Developed around two turbocharged 3,450 hp (2,570 kW) R-4360s driving pusher propellers, the XP-71 would have been the largest fighter aircraft built in the war.

[citation needed] As conditions changed and it was clear that Britain would continue to be available for forward bases, the requirement for the advanced fighter project led to the cancellation of the XP-71 in early 1942.