Abstract: An adaptive gain and phase controller for an autopilot for a flight vehicle, such as a hypersonic glide vehicle, that includes applying a reference excitation signal to the control system of a flight vehicle, measuring the response of the vehicle to that excitation signal, namely the gain and phase losses through airframe, and making adjustments to the gain and phase inputs to the autopilot based on those measurements. A high gain narrow bandpass filter is incorporated so that the test signal can be extracted from the airframe of the flight vehicle.