Most fighters grow around a cockpit and a pair of wings. The F-105 grew around a bomb bay. Kartveli’s team started from the volume needed to carry a Mark 28-class nuclear weapon internally — so that the aircraft stayed clean and fast on the low-level dash to the target — and then wrapped a Mach-2 airframe and the most powerful available engine around it. That is why the Thud ended up the largest single-seat, single-engine combat aircraft ever fielded, with an empty weight heavier than a fully loaded World War II fighter.

The irony is that the internal bay was almost never used for its intended purpose. Over Vietnam it usually carried a 1,500-litre fuel tank to extend the aircraft’s short legs, while the bombs hung outside on wing and centreline pylons. The Thud spent its whole combat career doing the opposite of what its shape was optimised for.

When North Vietnam fielded Soviet SA-2 surface-to-air missiles in 1965, the USAF had no answer. The response was the Wild Weasel: two-seat Thuds crewed by a pilot and an electronic-warfare officer whose job was to fly into the missile envelope, provoke a radar lock, and destroy the site. The crews’ grim motto was “First In, Last Out” — they arrived ahead of the strike package to clear the SAMs and stayed until the bombers had left. When the concept was first briefed, one EWO’s reaction — “You gotta be sh***ing me”, abbreviated YGBSM — became the community’s badge of honour. It was statistically the most dangerous flying job of the war.

The Thud was a strike aircraft, not a fighter — yet it is credited with 27.5 confirmed MiG kills over Vietnam, and all but a couple were scored with its internal 20 mm M61 Vulcan cannon rather than with missiles. Heavy and fast, a clean F-105 that had already dropped its bombs could accelerate away from a MiG-17 and, in the right setup, turn the tables with a gun pass. It was never going to win a low-speed turning fight, but on its own terms the bomber occasionally became the hunter.

The F-105D’s flyaway price is usually quoted at around $2.1 million in early-1960s dollars — roughly $20 million in today’s money and modest for a Mach-2 aircraft. But the meaningful cost of the Thud was measured in attrition, not procurement. With production having ended in 1964, every airframe shot down over North Vietnam was irreplaceable: the assembly lines were closed, and the fleet simply shrank with each mission. No reliable public cost-per-flight-hour figure exists for the type, and any precise dollar figure attached to it should be read as an estimate.