In 1962, the United States Navy began preliminary work on VAX (Heavier-than-air, Attack, Experimental), a replacement for the A-4 Skyhawk with greater range and payload. A particular emphasis was placed on accurate delivery of weapons to reduce the cost per target. The requirements were finalized in 1963 and in 1964, the Navy announced the VAL (Heavier-than-air, Attack, Light) competition. Contrary to USAF philosophy, which was to employ only supersonic fighter bombers such as the F-105 Thunderchief and F-100 Super Sabre, the Navy felt that a subsonic design could carry the most payload the farthest distance. One story illustrated that a "slow fat duck" could fly nearly as fast as a supersonic one, since carrying dozens of iron bombs also restricted its entry speed, but a fast aircraft with small wings and an afterburner would burn up a lot more fuel.

To minimize costs, all proposals had to be based on existing designs. Vought, Douglas Aircraft, Grumman, and North American Aviation responded. The Vought proposal was based on the successful F-8 Crusader fighter, having a similar configuration, but more short and stubby, with a rounded nose. It was selected as the winner on 11 February 1964, and on 19 March the company received a contract for the initial batch of aircraft, designated A-7. In 1965, the aircraft received the popular name Corsair II, after Vought's highly successful F4U Corsair of World War II.

Compared to the F-8 fighter, the A-7 had a shorter, broader fuselage. The wing was made larger, and the unique variable incidence wing of the F-8 was deleted. To achieve the required range, the A-7 was powered by a Pratt & Whitney TF30-P-6 turbofan producing 11,345 lbf (50.5 kN) of thrust, the same innovative combat turbofan produced for the F-111, but without the afterburner needed for supersonic speeds. Turbofans achieve greater efficiency by moving a larger mass of air at a lower velocity.

The aircraft was fitted with an AN/APQ-116 radar which was integrated into the ILAAS digital navigation system. The radar also fed a digital weapons computer which made possible accurate delivery of bombs from a greater stand-off distance, greatly improving survivability compared with faster platforms such as the F-4 Phantom II. It was the first U.S. aircraft to have a modern head-up display, now a standard instrument, which displayed information such as dive angle, airspeed, altitude, drift and aiming reticle. The integrated navigation system allowed for another innovation – the projected map display system (PMDS) which accurately showed aircraft position on two different map scales.

The A-7 enjoyed the fastest and most trouble free development period of any American combat aircraft since World War Two. The YA-7A made its first flight on 27 September 1965, and began to enter Navy squadron service late in 1966. The first Navy A-7 squadrons reached operation status on 1 February 1967, and began combat operations over Vietnam in December of that year.

Secretary of Defence Robert McNamara prodded the Air Force to adopt not only the hugely successful F-4 Phantom II, but also the Navy's A-7 Corsair as a low-cost follow-on to F-105s until the troubled F-111 came online, and as a close-air support replacement for A-1 Skyraider. On 5 November 1965, the USAF announced that it would purchase a version of the A-7, designated the A-7D, for Tactical Air Command. The Air Force ordered the A-7D with a fixed high speed refueling receptacle behind the pilot optimized for the KC-135's flying boom rather than the folding long probe of Navy aircraft. The most important difference from the preceding Navy versions was the adoption of the Allison TF41-A-1 turbofan, a license-built version of British Rolls-Royce Spey. With 14,500 lbf (64.5 kN) of thrust, the engine offered a considerable boost in performance. The M61 Vulcan cannon was selected in place of the twin single-barrel 20 mm cannon. In addition, avionics were upgraded, and the inflight refuelin g method was changed from probe-and-drogue to the boom. The YA-7D prototype with TF30 flew on 6 April 1968, with the first TF41 aircraft taking to the air on 26 September 1968. The aircraft were later updated to carry the Pave Penny laser spot tracker to add the capability to drop guided bombs. A total of 459 were built.

The Navy was so impressed with the performance gain of USAF A-7D that they ordered their own version with the TF41 engine and M61 cannon, the A-7E. The first prototype flew on 25 November 1968. In 1986, 231 A-7E were equipped to carry the LANA (Low-Altitude Night Attack) pod which projected amplified light image on the HUD and, in conjunction with radar, provided terrain following down to 460 mph (740 km/h) at 200 ft (60 m). A total of 529 were built (not counting 67 A-7Cs).

In 1985, the USAF requested proposals for a fast strike aircraft because of concerns that A-10 Thunderbolt II was too slow for interdiction. The design called for a new engine, either the Pratt & Whitney F100 or General Electric F110. LTV responded with the YA-7F, a supersonic version of A-7 powered by an F100-PW-220 with 26,000 lbf (116 kN) of thrust. To accommodate the new engine, the fuselage was lengthened about 4 ft (1.22 m). New fuselage sections were inserted in both the forward and aft fuselage - a 30 in (76 cm) section in front of the wing and an 18 in (46 cm) section behind the wing. The wing was strengthened and fitted with new augmented flaps, leading edge extensions and automatic maneuvering flaps. The vertical stabilizer height was increased about 10 in (25 cm). Ironically, but unsurprisingly given its antecedents, the end result resembled the F-8 Crusader from which the A-7 was originally derived. Two A-7Ds were modified, the first one flying on 29 November 1989 and breaking the sound barrier on its second flight. The second prototype flew on 3 April 1990. The project was cancelled in favor of the F-16 Fighting Falcon.

Production

Production of Corsairs continued through 1984, yielding a total of 1,569 aircraft built. The A-7 Corsair has the distinction of being the only United States single seat jet fighter/bomber of the 1960s that was designed, built, and deployed directly into the Vietnam War.