The Lockheed F-117 Nighthawk is a retired American single-seat, subsonic twin-engine stealth attack aircraft developed by Lockheed's secretive Skunk Works division and operated by the United States Air Force (USAF). It was the first operational aircraft to be designed with stealth technology.Work on what would become the F-117 was commenced in the 1970s as a means of countering increasingly sophisticated Soviet surface-to-air missiles (SAMs). During 1976, the Defense Advanced Research Projects Agency (DARPA) issued Lockheed with a contract to produce the Have Blue technology demonstrator, the test data from which validated the concept. On 1 November 1978, it was decided to proceed with the F-117 development program. A total of five prototypes would be produced; the first of which performed its maiden flight during 1981 at Groom Lake, Nevada. The first production F-117 was delivered in 1982, and its initial operating capability was achieved in October 1983. All aircraft were initially based at Tonopah Test Range Airport, Nevada.The aircraft's faceted shape (made from two-dimensional flat surfaces) heavily contributes to its relatively low radar cross-section of about 0.001 m2 (0.0108 sq ft). To minimize its infrared signature, it has a non-circular tail pipe that mixes hot exhaust with cool ambient air and lacks afterburners; it is also restricted to subsonic speeds as breaking the sound barrier would produce an obvious sonic boom that would increase both its acoustic and infrared footprints. While its performance in air combat maneuvering was less than that of most contemporary fighters, it was strictly an attack aircraft despite being commonly referred to as the "Stealth Fighter". For this reason, it is equipped with integrated sophisticated digital navigation and attack systems, targeting being achieved via a thermal imaging infrared system and a laser rangefinder/laser designator. It is aerodynamically unstable in all three aircraft principal axes and thus requir