The Hughes AIM-4 Falcon was the first operational guided air-to-air missile of the United States Air Force. Development began in 1946; the weapon was first tested in 1949. The missile entered service with the USAF in 1956. With the AIM-4's poor kill record rendering the F-4 ineffective at air-to-air combat, the fighters were modified to carry the AIM-9 Sidewinder missile instead. The Sidewinder was much more effective and continues to serve the armed forces of the United States to this day.