This paper discusses flight systems development and test issues of the Air Force's F-16 and A-1O Operational Flight Trainers (OFT) for flight controls, performance, and stability and control. Brief descriptions of the aircraft, simulators and their hardware, and flight systems software are presented. The basic design data base is described; simulator test techniques are presented; and some of the more interesting flight system simulation test problems and their resolutions are discussed. Probably the more basic reason for many of the A-10 OFT flight systems initial problems relates to the minimal involvement of user pilots during data development and flight system logic design operation. Conversely, the success of initial government flight systems testing of the F-16 OFT was aided by early user pilot involvement in system design and operation. This paper also contends that the greatest amount of transfer of training (simulator to aircraft) for flight systems operation and performance is obtained with a design philosophy which replicates cockpit features, visual cues, and the performance of the actual aircraft. The paper concludes with suggested future methods to improve simulation performance and test efficiency.