Douglas A-1 Skyraider AD-6 (A-1H)

The AD-6 was developed as an improved AD-4B, the version specialised in carrying nuclear weapons, and it became the most-produced single-seat attack Skyraider: Douglas built 713. Compared with its predecessor it gained improved equipment for low-level bombing, with a low/high altitude bomb director, three dive brakes and a centerline station stressed for 3,500 lb (1,600 kg) of ordnance up to 30 in (760 mm) in diameter, served by a combination 14 in and 30 in bomb ejector. It kept the AD-4's powerplant, an air-cooled 18-cylinder Wright R-3350-26WA Duplex-Cyclone radial of 2,700 hp (2,000 kW) driving a four-bladed Aeroproducts constant-speed propeller.

The AD-6 configuration is the one usually quoted as the reference for the whole family. With a crew of one, it was 11.84 m long, weighed 5,429 kg empty and reached 518 km/h at 5,500 m, with a cruising speed of 319 km/h, a range of 2,118 km and a service ceiling of 8,700 m. Its fixed armament was four 20 mm AN/M3 cannon with 200 rounds per gun, and its fifteen external hardpoints could carry 4,800 kg of bombs, torpedoes, mine dispensers, unguided rockets or gun pods. Only the AD-7 followed it, with the R-3350-26WB engine and structural improvements to increase wing fatigue life.

In 1962 the AD-6s were redesignated A-1H, and under that name they went to Vietnam. When American involvement began, the Skyraider was still the medium attack aircraft in many carrier air wings, although it was due to be replaced by the Grumman A-6 Intruder. Skyraiders from Constellation and Ticonderoga took part in the first US Navy strikes against North Vietnam on 5 August 1964, Operation Pierce Arrow, against fuel depots at Vinh. In October 1965 Commander Clarence J. Stoddard of VA-25, flying an A-1H, dropped a toilet along with his other munitions to mark the six millionth pound of ordnance dropped. Navy Skyraiders twice used their cannon to shoot down North Vietnamese MiG-17s: on 20 June 1965 with VA-25, the first gun kill of the Vietnam War, and on 9 October 1966 with VA-176. On 14 February 1968 the A-1H of Lieutenant (jg) Joseph P. Dunn of VA-25 was intercepted by Chinese fighters near Hainan Island during a ferry flight from Cubi Point to the carrier Coral Sea; it was the last Navy A-1 lost in the conflict.

The USAF also flew the A-1H in its special operations squadrons. On 1 September 1968 Lieutenant Colonel William A. Jones III, of the 602nd Special Operations Squadron at Nakhon Phanom in Thailand, led a flight of four A-1Hs escorting two helicopters sent to rescue the pilot of an F-4 Phantom downed near Dong Hoi, North Vietnam. On low passes across the valley he found the survivor and a multiple-barrel gun position near the top of a karst formation. He attacked it with cannon and rockets; on his second pass a round struck the Yankee extraction system rocket mounted behind his headrest and the cockpit caught fire. The damaged system only jettisoned the canopy without pulling him out, while his transmissions were blocked by other aircraft calling on him to bail out. Badly burned and with his radio transmitters disabled, Jones chose to fly back to base, landed and passed on the pilot's exact position before receiving medical treatment; the downed airman was rescued later that day. Jones survived, was promoted to colonel and died the following year in an aircraft accident in Virginia; President Richard Nixon presented his Medal of Honor to his widow on 6 August 1970.

The A-1H was also a mainstay of the Republic of Vietnam Air Force, which received former Navy A-1E and A-1H Skyraiders to replace its Grumman F8F Bearcats. The last aircraft transferred in late 1972 included 23 A-1H/Js, and the eleven Skyraiders that fled to Thailand in 1975 included five A-1Hs. A-1H 134600, operated by the South Vietnamese from 1965 to 1975, has been on display at the National Museum of the USAF since 2022.