The Republic F-105 Thunderchief, or company model AP-63, was conceived in 1951 as a nuclear strike aircraft with an internal bomb bay, but won renown for hauling bombs externally in a conventional war. Alexander Kartveli's design team originally intended a straight fuselage for the craft but, after seeing NACA data assembled by Richard Whitcomb, was won over by the wasp-waist or 'area rule' configuration which enhanced transonic flight performance. At first intended for the Allison J71 engine and powered in prototype form by the Pratt & Whitney J57, the F-105 attained its successes with the 7802kg thrust Pratt & Whitney J75-P-19W turbojet which provided 11113kg thrust with afterburning. Its mid-mounted wing, swept 60 degrees, the F-105 stood high on its tricycle gear and was a big, brutish machine, yet it conveyed an image of sleekness and grace slicing through the air. Development of the aircraft was by no means without its difficulties, and things had only begun when two J57-powered YF-105As commenced flying 22 October 1955, soon followed by 15 aircraft designated JF-105B and F-105B for test programmes.

Production F-105Bs, long delayed by development problems, began to roll from Republic's Farmingdale line during 1958 and the USAF accepted its first machine on 27 May 1958. The 335th Tactical Fighter Squadron, temporarily moved to Eglin AFB, Florida, began to work up in the new aircraft only to find that, given its complexity and production slippages, it would not become operational until 1960. Meanwhile, a two-seat strike variant, the F-105C, had reached the mock-up stage but was not built. Though technical problems persisted and critics were calling the 'Thud' a maintenance nightmare, Republic proceeded with the F-105D variant which afforded true, all-weather capability by introducing General Electric FC-5 fully integrated automatic flight fire-control system. The F-105D's fuselage was lengthened by 0.381m. Some 610 were manufactured, and first flight took place at Farmingdale 9 June 1959. The F-105D model soon equipped all three squadrons of the 4th Tactical Fighter Wing at Seymour Johnson AFB, North Carolina. United States Air Forces in Europe (USAFE) were the first overseas recipient of the F-105D, the 36th TFW at Bitburg AB, West Germany re-equipping from 12 May 1961 and the 49th TFW at Spangdahlem soon following. In the early 1960s, with a war growing in Asia, F-105Ds joined the 18th TFW at Kadena AFB, Okinawa.

The F-105D was by now a proven ordnance-carrier. With multiple ejector racks (MER), it could carry an impressive load of external fuel, ECM gear, and eight 340kg bombs on long-range missions. The F-105D could also operate with the Martin AGM-12 Bullpup air-to-surface missile, which was to prove remarkably ineffective against 'hard' targets in Vietnam and would be observed bouncing off the Thanh Hoa Bridge. In addition, the F-105D model could carry 70mm rocket pods, napalm canisters and the AIM-9 infra-red (IR) air-to-air missiles, while its integral M61A1 Gatling-type 20-mm cannon proved invaluable in the dual roles of air-to-air combat and air-to-ground strafing. A late-model variant of the F-105D was the F-105D T-Stick II fitted with additional avionics which bestowed all-weather bombing capability, housed in a prominent dorsal fairing extending along the spine of the fuselage to the tail.

The F-105E was another two-seat variant that was not developed. A two-seat Thunderchief was inevitable, however, and in May 1962 Republic proceeded with the F-105F. This model, which made its first flight 11 June 1963, was some 900kg heavier as well as slightly longer than earlier Thunderchiefs in order to accommodate the second crewman in tandem; 143 F-105Fs were delivered and 61 were later reconfigured for the electronic warfare or 'Wild Weasel' role in Vietnam, at first under their original designation and later as the F-105G.

The F-105D, F-105F and F-105G all fought in North Vietnamese skies, the F-104D model fighter-bomber so extensively that over half of the 610 built eventually fell to Hanoi's air defences. After withdrawal from South East Asia in 1969-70, the Thunderchief soldiered on in Reserve and Air National Guard units, eventually flying its final sortie in 1984. At one time no fewer than 14 USAF and 11 ANG squadrons operated the type, which was built to the extent of 833 examples. Perhaps because of its complexity, no F-105 was ever exported.