In 1978 Allen Paulson bought Grumman American and changed the name of the company to Gulfstream American. One of the reasons Paulson was interested in purchasing Gulfstream was to produce his dream project, the Hustler. The aircraft was powered by a turboprop engine in the front and a fanjet in the rear. The Hustler program suffered a number of delays. By May 1981, a Hustler 400 prototype (N400AJ, c/n 101, first flight 11-01-1978) had logged just 30 hours of test time. The Hustler 500 (N501GA, c/n 501), a redesigned version of the Hustler with wingtip tanks and changed air intake flew for the first time on January 26, 1981. The Hustler would never be certified and the program was ended in 1981.

The Hustler program was delayed because of the more and more focus from Gulfstream American on the GIII program but also because GA had designed a derivative of the Hustler, which the company hoped would be accepted by the US Air Force as a training aircraft. Called the Peregrine 600. The Peregrine was being developed in response to a request for the USAF's 'Next Generation Trainer' or 'NGT'. The first flight took place in Oklahoma on 22 May 1981. The Peregrine went through several different designs, including versions with tandem or side-by-side seating and different engine types and mounting. 

In June 1983 the Peregrine 600 (N600GA, c/n 601) made its appearance at the Paris Air Show, Le Bourget. The trainer aircraft crashed on November 23, 1983 at El Reno, Oklahoma during an evaluation flight with newly installed ailerons after 242 flight hour.

Gulfstream lost out in the competition to produce a military trainer. The Peregrine's military applications were abandoned in favor of  a further development of the business transport. The Commander Fanjet 1500 business jet made its first flight on January 14, 1983 and also made a visit to Le Bourget in June 1983 registered as N99881S (c/n 551). After cancellation of the Peregrine 600 military trainer the Fanjet 1500 designation was changed into Peregrine 550. In 1984 GA announced that it would go ahead with production. However production difficulties and insufficient orders resulted in the program being ended in 1985. The sole aircraft was withdrawn from use in march 1992. The Peregrine aircraft is now registered to Gulfstream Aerospace Corp., Savannah (GA) as Peregrine 550 (N84GP, c/n 551) and on display at the Oklahoma Science Museum in Oklahoma City (OK).