The AIM-9 Sidewinder is a heat-seeking, short-range, air-to-air missile carried mostly by fighter aircraft and recently, certain gunship helicopters. The missile entered service with United States Air Force in the early 1950s, and variants and upgrades remain in active service with many air forces after five decades. When a Sidewinder missile is being launched, NATO pilots use the brevity code Fox Two in radio communication, as with all "heat-seeking" missiles.
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 kills worldwide to date.
The missile was designed to be simple to upgrade. It has been said that the design goals for the original Sidewinder were to produce a reliable and effective missile with the "electronic complexity of a table model radio and the mechanical complexity of a washing machine"—goals which were well accomplished in the early missiles. The United States Navy hosted a 50th anniversary celebration of its existence in 2002. Boeing won a contract in March 2010 to support Sidewinder operations through 2055, guaranteeing that the weapons system will remain in operation until at least that date. Air Force Spokeswoman Stephanie Powell noted that due to its relative low cost, versatility, and reliability it is "very possible that the Sidewinder will remain in Air Force inventories through the late 21st century."
Sidewinder is the common name of Crotalus cerastes, a venomous rattlesnake which uses infrared sensory organs to hunt warm-blooded prey. Early versions of the missile tended to perform zig-zagging course corrections during the early part of their flight path, following a trajectory that resembled the sidewinding motion of the snake.