The XF-90, like the McDonnell XF-88, was developed to meet a USAF requirement for a long-range "Penetration Fighter." Two prototype aircraft were built (S/N 46-687 and 46-688). The first was powered by two Westinghouse J34 turbojets without afterburners, but these proved inadequate. The second aircraft was adapted for afterburning J34s and had better, but not great, performance. The outbreak of the Korean War prompted to USAF to seek increased production of currently available aircraft, and the XF-90 never entered production.
The XF-90 had two unusual features. The first was the location of the cannon ports located below the engine air intakes in a horizontal row, three on each side. The second was the variable incidence empennage. The vertical stabilizer could be tilted back and forth along the longitudinal axis for horizontal stabilizer adjustment.
TECHNICAL NOTES: Engines: Two Westinghouse J34-WE-15 turbojets of 4,100 lbs. thrust each with afterburner Armament: Designed for six 20 mm cannons, eight 5-inch HVAR rockets and up to 2,000 lbs. of bombs Maximum speed: 665 mph Cruising speed: 473 mph Range: 2,300 miles Service ceiling: 39,000 ft. Span: 40 ft. 0 in. Length: 56 ft. 2 in. Height: 15 ft. 9 in. Weight: 27,200 lbs. loaded Crew: One