The XF-90 was developed to meet a USAF requirement for a long-range penetration fighter. Two prototype aircraft were built. 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.