This paper presents the development of a GPS/INS sensor fusion simulation environment through the use of WVU YF-22 flight data. Noise on the GPS measurements was modeled using satellite ephemeral data as well as recorded flight data. The noise characteristics of the IMU were determined from an Allan variance approach. The GPS and IMU noise models were implemented in the WVU formation flight simulator, which includes an EKF-based sensor fusion algorithm to estimate the position, velocity, and attitude of the aircraft. Using both simulated and recorded flight data, attitude estimation results were used to evaluate the accuracy of the GPS and IMU measurement noise models, since the flight data includes a high quality measurement of the roll and pitch angles from a mechanical vertical gyroscope. It was determined from this analysis that the simulator includes a realistic model of the noise present in recorded flight data, which allows for validation and analysis of sensor fusion algorithms.