The AIM-120 Advanced Medium-Range Air-to-Air Missile (AMRAAM) (/æmræm/ AM-ram) is an American beyond-visual-range air-to-air missile capable of all-weather day-and-night operations. It uses active transmit-receive radar guidance instead of semi-active receive-only radar guidance; as an active seeker missile, NATO pilots thus use the brevity code "Fox Three" when firing the AIM-120.

The AMRAAM largely replaced the AIM-7 Sparrow as the principal beyond-visual-range air-to-air missile in U.S. inventory. As of 2008^[update] more than 14,000 had been produced for the United States Air Force, the United States Navy, and 33 international customers. The AMRAAM has been used in several engagements, achieving 16 air-to-air kills in conflicts over Iraq, Bosnia, Kosovo, India, and Syria. In the long term, it is expected to eventually be replaced by the long range AIM-260 JATM in U.S. service and the MBDA Meteor in some European countries.

The AIM-7 Sparrow medium range missile (MRM) was purchased by the US Navy from original developer Hughes Aircraft in the 1950s as its first operational air-to-air missile with "beyond visual range" (BVR) capability. With an effective range of about 12 miles (19 km), it was introduced as a radar beam-riding missile and then it was improved to a semi-active radar guided missile which would home in on reflections from a target illuminated by the radar of the launching aircraft. It was effective at visual to beyond visual range. The early beam riding versions of the Sparrow missiles were integrated onto the McDonnell F3H Demon and Vought F7U Cutlass, but the definitive AIM-7 Sparrow was the primary weapon for the all-weather McDonnell Douglas F-4 Phantom II fighter/interceptor, which lacked an internal gun in its U.S. Navy, U.S. Marine Corps, and early U.S. Air Force versions. The F-4 carried up to four AIM-7s in built-in recesses under its belly.

Designed for use against non-maneuvering targets such as bombers, the missiles initially performed poorly against fighters over North Vietnam, and were progressively improved until they proved highly effective in dogfights. Together with the short-range, infrared-guided AIM-9 Sidewinder, they replaced the AIM-4 Falcon IR and radar guided series for use in air combat by the USAF as well. A disadvantage to semi-active homing was that only one target could be illuminated by the launching fighter plane at a time. Also, the launching aircraft had to remain pointed in the direction of the target (within the azimuth and elevation of its own radar set) which could be difficult or dangerous in air-to-air combat.

An active-radar variant called the Sparrow II was developed to address these drawbacks, but the U.S. Navy pulled out of the project in 1956. The Royal Canadian Air Force, which took over development in the hopes of using the missile to arm their prospective Avro Canada CF-105 Arrow interceptor, soon followed in 1958. The electronics of the time simply could not be miniaturized enough to make Sparrow II a viable working weapon. It would take decades, and a new generation of digital electronics, to produce an effective active-radar air-to-air missile as compact as the Sparrow.

The US Navy later developed the AIM-54 Phoenix long-range missile (LRM) for the fleet air defense mission. It was a large 1,000 lb (500 kg), Mach 5 missile designed to counter cruise missiles and the bombers that launched them. Originally intended for the straight-wing Douglas F6D Missileer and then the navalized General Dynamics–Grumman F-111B, it finally saw service with the Grumman F-14 Tomcat, the only fighter capable of carrying such a heavy missile. The Phoenix was the first US fire-and-forget, multiple-launch, radar-guided missile: one which used its own active guidance system to guide itself without help from the launch aircraft when it closed on its target. This, in theory, gave a Tomcat with a six-Phoenix load the unprecedented capability of tracking and destroying up to six targets beyond visual range, as far as 100 miles (160 km) away—the only US fighter with such capability.

A full load of six Phoenix missiles and their 330 lb (150 kg) dedicated launchers exceeded a typical Vietnam-era bomb load. Its service in the US Navy was primarily as a deterrent, as its use was hampered by restrictive rules of engagement in conflicts such as 1991 Gulf War, Southern Watch (enforcing no-fly zones), and Iraq War. The US Navy retired the Phoenix in 2004 in light of availability of the AIM-120 AMRAAM on the McDonnell Douglas F/A-18 Hornet and the pending retirement of the F-14 Tomcat from active service in late 2006.

The Department of Defense conducted an extensive evaluation of air combat tactics and missile technology from 1974 to 1978 at Nellis AFB using the F-14 Tomcat and F-15 Eagle equipped with Sparrow and Sidewinder missiles as the blue force and aggressor F-5E aircraft equipped with AIM-9L all-aspect Sidewinders as the red force. This joint test and evaluation (JT&E) was designated Air Combat Evaluation/Air Intercept Missile Evaluation (ACEVAL/AIMVAL).^{[citation needed]} A principal finding was that the necessity to produce illumination for the Sparrow until impact resulted in the red force's being able to launch their all-aspect Sidewinders before impact, resulting in mutual kills. What was needed was Phoenix-type multiple-launch and terminal active capability in a Sparrow-size airframe. This led to a memorandum of agreement (MOA) with European allies (principally the UK and Germany for development) for the US to develop an advanced, medium-range, air-to-air missile with the USAF as lead service.