The Air Force deployed AIM-4 in May 1967 during the Vietnam War on the new F-4D Phantom II, which carried it on the inner wing pylons and was not wired to carry the AIM-9 Sidewinder. The missile's combat performance was very poor. The Falcon, already operational on Air Defense Command aircraft, was designed to be used against bombers, and its slow seeker cooling times (as much as six or seven seconds to obtain a lock on a target) rendered it largely ineffective against maneuvering fighters. Moreover, it could only be cooled once. Limited coolant supply meant that once cooled, the missile would expend its supply of liquid nitrogen in two minutes, rendering it useless on the rail. The missile also had a small warhead, and lacked proximity fusing. As a result, only five kills were scored, all with the AIM-4D version. (The Falcon was also experimentally fired by the F-102 Delta Dagger against ground targets at night using its infrared seeker.)