NASA 840 is an F-18 that was used to carry out high angle of attack research. It was modified with a thrust vectoring system around the exhaust nozzles of each engine. The system, linked to the aircraft's flight control system, moves a set of three paddles on each engine to redirect thrust for directional control and increased maneuverability at angles of attack near 70 degrees. Research flights, with the thrust vectoring system intalled, began during the summer of 1991 at the Dryden Flight Research Center, Edwards, California, and ended May 29, 1996. Data from the F-18 High Alpha Research Vehicle (HARV) program produced information to validate computer codes and wind tunnel results and led to design methods providing better performance in future aircraft.