The F-117 was based on the Have Blue technology demonstrator. The Nighthawk was the first operational aircraft to be designed around stealth technology. Its maiden flight took place in 1981 at Groom Lake, Nevada, and the aircraft achieved initial operating capability status in 1983. The Nighthawk was shrouded in secrecy until it was revealed to the public in 1988. Of the 64 F-117s built, 59 were production versions, with the other five being prototypes. The F-117 was widely publicized for its role in the Persian Gulf War of 1991. Although it was commonly referred to as the "Stealth Fighter", it was strictly a ground-attack aircraft. F-117s took part in the conflict in Yugoslavia, where one was shot down by a surface-to-air missile (SAM) in 1999; it was the only Nighthawk to be lost in combat. The U.S. Air Force retired the F-117 in April 2008, primarily due to the fielding of the F-22 Raptor. Despite the type's retirement, a portion of the fleet has been kept in airworthy condition, and Nighthawks have been observed flying in 2020. For details of development, design and operational history, click here. Two variants were proposed by never ordered.