Developed in the 1960s by General Dynamics under Robert McNamara's TFX Program, the F-111 pioneered variable-sweep wings, afterburning turbofan engines, and automated terrain-following radar for low-level, high-speed flight.

Being relatively expensive to maintain amid post-Cold War budget cuts, the USAF elected to retire its F-111 fleet during the 1990s; the last F-111Fs were withdrawn in 1996 while the remaining EF-111s also departed in 1998.

The RAAF continued to operate the type up until December 2010, when the last F-111C was retired; its role was transitioned to the Boeing F/A-18E/F Super Hornet as an interim measure until the Lockheed Martin F-35 Lightning II became available.

Besides greatly damaging US–Soviet relations, the incident showed that the Soviet Union had developed a surface-to-air missile that could reach aircraft above 60,000 feet (18,000 meters).

[5] A simpler variable geometry wing configuration with the pivot points farther out from the aircraft's centerline was reported by NASA in 1958, which made swing-wings viable.

[8] In June 1960, the USAF issued specification SOR 183 for a long-range interdiction/strike aircraft able to penetrate Soviet air defenses at very low altitudes and high speeds.

[16][17] Variable geometry offered high speeds, and maneuverability with heavier payloads, long range, and the ability to take off and land in shorter distances.

[18] The aircraft sought by the two armed services shared the need to carry heavy armament and fuel loads, feature high supersonic speed, twin engines and two seats, and probably use variable geometry wings.

[21] In June 1961, Secretary McNamara ordered the go ahead of Tactical Fighter Experimental (TFX), despite USAF and Navy efforts to keep their programs separate.

[22][23] According to aviation author Peter E. Davis, military officials were disconcerted by McNamara's focus on compromised requirements for financial reasons.

[23][29][31] On 1 May 1964, the definitized contract was issued for the program, including flight testing, spares, ground equipment, training devices, static and fatigue test data, and the production of an initial 23 F-111 aircraft; it was structured as a fixed price incentive fee (FPIF) contract with a ceiling price of $529 million along with provisions for deficiency correction amongst other operational clauses and performance criteria.

The F-111B's nose was 8.5 feet (2.59 m) shorter as the aircraft could fit on existing carrier elevator decks, and had 3.5-foot-longer (1.07 m) wingtips to improve on-station endurance time; it also carried an AN/AWG-9 Pulse-Doppler radar to guide its AIM-54 Phoenix missiles.

[32] On 15 October 1964, the first test F-111A was rolled out of Plant 4 of General Dynamics' facility in Fort Worth, Texas; it was powered by YTF30-P-1 turbofans and used a set of ejector seats as the escape capsule was not yet available.

[39] Lasting for 22 minutes, less than planned due to a flap malfunction, this initial flight was considered to be satisfactory overall; category I testing commenced immediately thereafter.

[42] The cause of the cost rises has been attributed, at least partially, to a directive issued to General Dynamics to incorporate improved avionics as well as to work on strategic bomber and aerial reconnaissance variants of the aircraft, the latter of which was eventually cancelled.

[77] FB-111As could carry the same conventional ordnance as the tactical variants, but their wing pylons were more commonly used for either fuel tanks or strategic nuclear gravity bombs.

It turned out that the third loss was traced to a failure of a hydraulic control-valve rod for the horizontal stabilizer which caused the aircraft to pitch up uncontrollably.

[105] The Australian government ordered 24 F-111C aircraft to replace the RAAF's English Electric Canberras in the bombing and tactical strike role.

Twenty-four Boeing F/A-18E/F Super Hornets were procured as an interim replacement as the Lockheed Martin F-35 Lightning II program was delayed.

[125] In 1982, four surviving F-111As were provided to Australia as attrition replacements and modified to F-111C standard, including its longer-span wings and reinforced landing gear.

[136] The F-111D was an upgraded F-111A equipped with newer Mark II avionics, more powerful engines, improved intake geometry, and an early glass cockpit.

[140] The F-111D used the new Triple Plow II intakes, which were located four inches (100 mm) further away from the airframe to prevent engine ingestion of the sluggish boundary layer air that was known to cause stalls in the TF30 turbofans.

[152] The F-111F was the final variant produced for Tactical Air Command, with a modern, but less expensive, Mark IIB avionics system, more powerful TF30-P-100 engine, and strengthened wing carry-through box.

[160] The F-111F's Mark IIB avionics suite used a simplified version of the FB-111A's AN/APQ-144 radar, which lacked some operating modes but added a new 2.5 mi (4.0 km) display ring.

[161] In the early 1980s, the F-111F began to be equipped with the AVQ-26 Pave Tack forward looking infrared (FLIR) and laser designator system, which enabled the use of precision laser-guided munitions and was mounted in the internal weapons bay.

Other changes included weapons bay modifications, addition of a centerline pylon, a retractable refueling probe, provisions for a reconnaissance pallet, and a higher gross weight with the use of FB-111A landing gear.

Ultimately however, the two F-111Ks were never operated as test aircraft – in July 1968, almost exactly a year after the first airframe began construction, the USAF decided not to take them over, and General Dynamics were ordered to use them for component recovery.

[175][174] Fuel capacity was increased by 585 gallons (2,214 L) and strengthened landing gear permitted a higher maximum takeoff weight of 119,250 lb (54,105 kg).

The next was a lengthened "FB-111H" fitted with more powerful General Electric F101 turbofan engines, a 12 ft 8.5 in longer fuselage and redesigned fixed intakes.

In May 1998, the USAF withdrew the final EF-111As from service, placing them in storage at Aerospace Maintenance and Regeneration Center (AMARC) at Davis–Monthan Air Force Base.