In 1956, based on the commercialized CJ805-3 version of the military J79 turbojet then powering the Convair 880, GE began development of an aft fan engine, the J79-X220, later designated CJ-805-23. This uncomplicated and low cost development increased take-off thrust by 40 percent, lowered specific fuel consumption by 15 percent, and reduced takeoff and landing noise. The engine became the first U.S. turbofan and, on the Convair 990 in the 1960s, the first in the world to enter airline service.

Because American Airlines wanted a competitive edge, it had asked Convair to develop a larger and faster version of the Model 880. Although the Model 990's design speed was Mach 0.91, just under the speed of sound, relatively few sales were made of it or the Model 880, and a demonstration of the C805-23 on a Caravelle airliner was also an unsuccessful venture. However, the engine did provide GE experience for the corporation's future commercial aircraft engine business.