In the 1960s, the United States began developing a supersonic transport (SST), the Boeing 2707. General Electric’s GE4 was intended to power the 300-seat airliner to a speed of Mach 2.7. Based on previous military engines, the GE4 was the largest straight turbojet engine ever built. Besides its powerful thrust and ability to withstand high temperatures associated with supersonic flight, it had a variable area exhaust nozzle with an integral thrust reverser.

Ground tests began in 1968. However, mainly because of economic and environmental concerns, the U.S. Senate canceled the American SST in 1971 by a 49 to 48 vote. The smaller Mach 2 Anglo-French Concorde, with its Rolls-Royce Olympus engines, was the only SST that achieved sustained commercial operation.