This paper presents a flying qualities evaluation of an L1 adaptive flight control law implemented on Calspan’s variable-stability Learjet aircraft. The variable-stability capability of the aircraft was used to alter its apparent dynamics while in flight, allowing the validation of the L1 flight control law against a set of off-nominal aircraft configurations. All of these off-nominal configurations were opaque to the control law, and no fault detection and isolation methods were employed. The results demonstrated that the L1 flight control law was able to significantly restore the flying qualities of a baseline Learjet model. The flight tests were conducted by the U.S. Air Force Test Pilot School at the Edwards Air Force Base, CA. The companion paper  presents the results of a handling qualities assessment, which complement the flight test results presented here.