The AIM-9 Sidewinder is a supersonic, heat-seeking, air-to-air missile carried by fighter aircraft. It has a high-explosive warhead and an active infrared guidance system.

The Sidewinder was developed by the US Navy for fleet air defence and was adapted by the US Air Force for fighter aircraft use. Early versions of the missile were extensively used in the Southeast Asian conflict. In September 1958 Chinese Nationalist F-86s fired the first Sidewinder air-to-air missiles to down 11 communist Chinese MiG-17s over the Formosa Straits.

Until that time, aircraft defensive means were primarily limited to pilots and tail gunners firing small calibre ammunition in dog-fight situations.

The AIM-9 has a cylindrical body with a roll-stabilizing rear wing/rolleron assembly. Also, it has detachable, double-delta control surfaces behind the nose that improve the missile's manoeuvrability. Both rollerons and control surfaces are in a cross-like arrangement.

The missile's main components are an infrared homing guidance section, an active optical target detector, a high-explosive warhead, and a rocket motor.

The infrared guidance head enables the missile to home on target aircraft engine exhaust. An infrared unit costs less than other types of guidance systems, and can be used in day/night and electronic countermeasures conditions.

The infrared seeker also permits the pilot to launch the missile, then leave the area or take evasive action while the missile guides itself to the target.