The author shows how judicious use of simulation in support of flight test can be used to leverage the flight test available in many programs to more adequately cover the complex test requirements of modern systems. The simulation facility is designed around the multiplex data bus structure found in all modern U.S. aircraft. This architecture makes the simulation problem easier but is not a necessary condition for the application of these techniques to support flight test. However, for non-multiplex bus systems the simulation is by nature more single purpose and the difficulty in changing the simulation facility from one aircraft type to another is greatly increased. The Naval Air Test Center is committed to the use of simulation to support the flight test requirements for all current and future Navy aircraft. We use the facility today to support FA-18 and AV-8B avionics system testing. The facility is being expanded to also support flight system and flight control computer testing for the FA-18, AV-8B, F-4S, F-14, and X-29 aircraft.