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Did you know that at one time, the General Dynamics-Grumman F-111B was considered as a replacement for the F-4 Phantom II as a long-range carrier-based interceptor? This would be part of the Tactical Fighter Experimental (TFX) in conjunction with the USAF to produce a common fighter for the two services and intended to perform a variety of missions. Its innovations included variable-geometry wings, afterburning turbofans and a long-range radar and missile weapons system.

The F-111B was part of the 1960s TFX program. The USAF's Tactical Air Command (TAC) was largely concerned with the fighter-bomber and deep strike/interdiction roles; their version of the aircraft would be a follow-on to the F-105 Thunderchief fighter-bomber. In June 1960, the USAF issued a specification for a long-range interdiction and strike aircraft able to penetrate Soviet air defenses at very low altitudes and very high speeds to deliver tactical nuclear weapons against crucial targets.

Meanwhile, the U.S. Navy sought a long-range, high-endurance interceptor to defend its aircraft carrier battle groups against long-range anti-ship missiles launched from Soviet jet bombers, such as the Tupolev Tu-16, Tupolev Tu-22, and Tupolev Tu-22M, along with submarines. The Navy needed a Fleet Air Defense (FAD) aircraft with a more powerful radar, and longer range missiles than the F-4 Phantom II to intercept both enemy bombers and missiles.

The Air Force and Navy requirements appeared to be different. However, on 14 February 1961, Secretary of Defense, Robert McNamara, formally directed that the services study the development of a single aircraft that would satisfy both requirements. Early studies indicated the best option was to base the Tactical Fighter Experimental (TFX) on the Air Force requirement and a modified version for the Navy. In June 1961, Secretary McNamara ordered the go ahead on TFX despite Air Force and the Navy efforts to keep their programs separate.

The USAF and the Navy could only agree on swing-wing, two seat, twin engine design features. The USAF wanted a tandem seat aircraft for low level penetration, while the Navy wanted a shorter, high altitude interceptor with side by side seating. Also, the USAF wanted the aircraft designed for 7.33 g with Mach 2.5 speed at altitude and Mach 1.2 speed at low level with a length of approximately 70 ft (21 m). The Navy had less strenuous requirements of 6 g with Mach 2 speed at altitude and high subsonic speed (approx. Mach 0.9) at low level with a length of 56 ft (17.1 m). The Navy also wanted a 48-inch (120 cm) radar dish for long range and a maximum takeoff weight of 50,000 pounds (23,000 kg). So McNamara developed a basic set of requirements for TFX based largely on the Air Force's requirements. He changed to a 36-inch (91 cm) dish for compatibility and increased the maximum weight to approximately 60,000lbs (27,200 kg) for the Air Force version and 55,000lbs (24,900 kg) for the Navy version. Then on 1 September 1961 he ordered the USAF to develop it.

The Air Force F-111A and Navy F-111B variants used the same airframe structural components and TF30-P-1 turbofan engines. They featured side by side crew seating in an escape capsule as required by the Navy, versus individual ejection seats. The F-111B's nose was 8.5 feet (2.59 m) shorter due to its need to fit on existing carrier elevator decks, and had 3.5 feet (1.07 m) longer wingspan to improve on-station endurance time. The Navy version would carry an AN/AWG-9 Pulse-Doppler radar and six AIM-54 Phoenix missiles. The Air Force version would carry the AN/APQ-113 attack radar and the AN/APQ-110 terrain-following radar and air-to-ground ordnance.

Lacking experience with carrier-based fighters, General Dynamics teamed with Grumman for assembly and test of the F-111B aircraft. In addition, Grumman would also build the F-111A's aft fuselage and the landing gear. The first test F-111A was powered by YTF30-P-1 turbofans and used a set of ejection seats, since the escape capsule was not yet available. It first flew on 21 December 1964. The first F-111B was also equipped with ejection seats and first flew on 18 May 1965. To address stall issues in certain parts of the flight regime, the F-111's engine inlet design was modified in 1965–66, ending with the "Triple Plow I" and "Triple Plow II" designs. The F-111A achieved a speed of Mach 1.3 in February 1965 with an interim intake design.

The weight goals for both F-111 versions proved to be overly optimistic. Excessive weight plagued the F-111B throughout its development. The prototypes were far over the requirement weight. Design efforts reduced airframe weight but were offset by the addition of the escape capsule. The additional weight made the aircraft underpowered. Lift was improved by changes to the wing control surfaces. A higher thrust version of the engine was planned.

While the F-111 Aardvark would be adopted by the USAF as a strike fighter, the F-111B suffered development issues and changing Navy requirements for an aircraft with maneuverability for dogfighting. The F-111B was not ordered into production and the F-111B prototypes were used for testing before being retired. The F-111B would be replaced by the smaller and lighter Grumman F-14 Tomcat, which carried over the engines, AWG-9/Phoenix weapons system, and similar swing-wing configuration.