Sub-scale flight: demonstrators have been used in the past to verify overall conceptual design in a limited quantitative manner. With the advent of small, reliable turbojet units, lightweight moldless fiberglass, graphite and foam plastic composite construction, and effective, compact flight test instrumentation, it is now possible to conduct early, low-cost flight test programs to validate a concept and save time and considerable flight test expense of the later full-scale development program.Fairchild Republic Company (FRC), in the course of developing its Next Generation Trainer (NGT) configuration, contracted the services of Ames Industrial Corp. to produce a flight demonstrator, with the assistance of Rutan Aircraft Factory and Flight Systems, Inc., to provide design, flight test and instrumentation services.The approach was highly successful in terms of cost, schedule and results. The overall program required approximately the same cost and schedule to accomplish as would a wind tunnel test program using a complex powered wind tunnel model. Comprehensive results were obtained under representative dynamic flight conditions that could not be accurately simulated in a wind tunnel. The results of the flying qualities tests provided close correlation with analytical estimates. In particular, natural stall warning was exhibited, as well as excellent stall characteristics, and satisfactory operation in strong crosswinds during takeoff and landing. Considerable reduction in program cost and in technical and schedule risk of a full-scale NGT development program is expected as a result of the demonstrator program.