Developed in the 1960s by General Dynamics, the F-111 pioneered variable-sweep wings, afterburning turbofan engines, and automated terrain-following radar for low-level, high-speed ¿ight. Its design in¿uenced later variable-sweep wing aircraft, and some of its advanced features have become commonplace. Being relatively expensive to maintain amid post-Cold War budget cuts, the USAF elected to retire its F-111 ¿eet during the 1990s.