 The high angle of attack area of flight was protected by a stick shaker system to warn the pilot of an approaching stall, and if this was ignored, a stick pusher system would pitch the aircraft's nose down to a safer angle of attack; this was often overridden by the pilot despite flight manual warnings against this practice.Another serious design issue that the aircraft encountered was T-tail flutter; Dick Heppe, who served as the initial project aerodynamics engineer for the F-104 program, recalled that "without question, the single most difficult technical challenge encountered in the XF-104 and F-104A development programs was the catastrophic flutter problem of the unique T-tailed empennage configuration.