Planned in 1963 as the successor to the Douglas A-4 Skyhawk for the US Navy and Marines, the A-7 Corsair II proved so effective that it was also chosen by the USAF to replace the F-100 Super Sabre and F-105 Thunderchief. The prototype flew for the first time on September 27, 1965, and production commenced on 199 of the A-7A version. This was followed by the more powerful A-7B (196 machines, first flight February 6, 1968). The variant designed for the USAF was the A-7D, which took off on April 5 furnished with a different kind of engine and modified both with regard to armament and electronics. Deliveries of the 459 models of the A-7D which had been ordered took place from September 1970 to December 1976. In 1969 a new version was produced for the US Navy, the A-7E, which became the principal type built (after the first 67 machines, known as A-7C), with 529 planes up to March 1981. Among minor variants were the TA-7C and the A-7K, two-seater trainers for possible operational use by the US Navy and the US Air National Guard; and the A-7H and A-7P for Greece and Portugal. It was much used in Vietnam; the first A-7As received their baptism of fire on December 4, 1967.