This paper presents a handling qualities assessment of Calspan’s variable-stability Lear- jet aircraft augmented with an L1 adaptive flight control law. 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, some of them with aggressive tendencies to adverse pilot-aircraft interaction. All of these off-nominal configurations were opaque to the control law, and no fault detection and isolation methods were employed. The results demonstrate that the L1 flight control law was able to recover consistent and safe handling qualities across all configurations. The evaluation also included a series of straight-in landings with two different aircraft configurations. Results which demonstrate the ability of the L1 flight control law to significantly restore the flying qualities of a baseline Learjet model are presented in the companion paper . The flight tests were conducted by the U.S. Air Force Test Pilot School at Edwards Air Force Base, CA.