The Phantom II was first developed for U.S. Navy fleet defense. The U. S. Air Force’s first version, the F-4C, made its first flight in May 1963, and production deliveries began soon after. In 1965, the U. S. Air Force sent its first F-4Cs to Southeast Asia where they flew air-to-air combat missions against North Vietnamese fighters. The aircraft carried out secondary mission of attacking key ground targets. In its air-to-ground role, the F-4C could carry twice the payload of a WW2 II B-17.