McNamara’s insistence on a joint USAF/USN aircraft made the TFX one of the most politically charged procurement fights of the Cold War. The Air Force wanted a heavy, fast interdiction striker; the Navy wanted a loitering fleet-defence interceptor to carry the big AIM-54 Phoenix missile. Forcing both roles into one airframe produced an aircraft that was a reasonable Air Force striker and an unworkable Navy fighter.

The Boeing design was preferred by the evaluation boards, but the General Dynamics bid won on grounds of commonality — a decision that drew a Senate investigation. The naval F-111B, built with Grumman, came out overweight and underpowered for carrier operations; it was cancelled in 1968 after seven airframes. Crucially, the Navy kept the best ideas — the variable-sweep wing, the TF30 engine, the AWG-9 radar and the Phoenix missile — and Grumman recycled them into the F-14 Tomcat. The F-111, in a sense, gave birth to its own replacement in Navy service while going on to a long and effective Air Force career.

The heart of the F-111 as a weapon was its automatic terrain-following radar (TFR). Two independent radar channels scanned the ground ahead and fed the autopilot, which pitched the aircraft up and over ridges and back down into valleys without the pilot touching the stick — at 200 ft and 480 knots or more, in total darkness or thick weather. It was a genuinely nerve-shredding way to fly: the system was designed to command a climb, not a dive, if it ever failed, so a fault meant the jet zoomed skyward rather than into a hillside. This capability let a single Aardvark penetrate defences that would have shredded a formation of conventional bombers, and it made the type the West’s premier all-weather night striker for two decades.

The F-111 did not use conventional ejection seats. Instead the entire two-seat cockpit section was a self-contained escape capsule. Pulling the handle fired an explosive guillotine that severed the module from the fuselage; a rocket motor blasted it clear, and a large parachute lowered the whole capsule — crew still strapped inside, pressurised and protected — to the ground or water. Airbags cushioned the landing, and the sealed module could float, acting as a life raft at sea. The system worked across the entire flight envelope, from the runway to supersonic speed at altitude, and saved numerous crews over the type’s career, though it was heavy and complex compared with ordinary seats.

The F-111 was capable but famously expensive to keep flying. Its complex swing-wing mechanism, terrain-following radar and dense avionics demanded heavy maintenance: one widely repeated figure holds that the type made up around nine percent of Tactical Air Command’s fleet yet consumed roughly 25 percent of its maintenance budget. No single reliable public cost-per-flight-hour figure exists for the type, and unit-cost numbers vary with variant and accounting method — the low-eight-figure dollar range often quoted should be treated as an approximation, not a sourced flyaway price. Those high running costs, more than any lack of capability, helped drive the F-111 out of US service in the 1990s in favour of the cheaper-to-operate F-15E Strike Eagle and B-1B Lancer.