The 990 entered production in 1961. One interesting change compared to the 880 was the addition of large bulges on the upper wing, in order to make the plane follow the area rule more closely, and thus reduce drag. This allowed the heavier 990 to gain a small amount of speed over the 880, cruising at about Mach 0.91. The inner set of bumps also served a secondary role as fuel dump for the fuel tanks in the fuselage. The engines were also changed to the uprated General Electric CJ-805-23's, which were unique in that they used a fan stage at the rear of the engine in addition to the small one found in the original 805-3's. Like the 880, 990s were later modified with a "raceway" added to the top of fuselage to hold the wiring for additional instrumentation.
The 990s market niche was soon to be destroyed entirely by the Boeing 727, and by the time the line was shut down in 1963 only 37 had been produced, bringing General Dynamic's entire production of commercial aircraft to 102 airframes.