The AIM-9 Sidewinder is a short-range air-to-air missile developed by the United States Navy in the 1950s. Entering service in 1956, variants and upgrades remain in active service with many air forces after six decades. The United States Air Force purchased the Sidewinder after the missile was developed by the United States Navy at China Lake, California. It is one of the most widely used missiles in the world: The AIM-9 is equipping most western-aligned air forces, as well as indirectly many nations which received the Soviet K-13 missile, a reverse-engineered copy of the AIM-9.
The majority of Sidewinder variants utilize infrared homing for guidance; the AIM-9C variant used semi-active radar homing and served as the basis of the AGM-122 Sidearm anti-radar missile. The Sidewinder is the most widely used missile in the West, with more than 110,000 missiles produced for the U.S. and 27 other nations, of which perhaps one percent have been used in combat. It has been built under license by some other nations including Sweden. The AIM-9 is one of the oldest, least expensive, and most successful air-to-air missiles, with an estimated 270 aircraft kills in its history of use. American and NATO pilots use the brevity code FOX-2. In addition to fixed-wing aircraft, some modern helicopters, such as the AH-1 SuperCobra, can be equipped with the Sidewinder.