The XF8B-1 was, at the time, the largest and heaviest single-seat, single-engine fighter developed in the United States.

It was powered by a single 3,000 hp (2,200 kW) Pratt & Whitney XR-4360-10 four-row 28-cylinder radial engine, driving two three-bladed contra-rotating propellers.

The final configuration was a large but streamlined design, featuring a bubble canopy, sturdy main undercarriage that folded into the wings, and topped by a variation on the B-29 vertical tail.

[3] Although testing of the promising XF8B concept continued into 1946 by the USAAF and 1947 by the US Navy, the end of the war in the Pacific and changing postwar strategy required that Boeing concentrate on building large land-based bombers and transports.

This occurred just as first shift was ending, and as many workers watched from the Plant 2 steps, the XF8B-1 bellied onto the concrete of Boeing Field.