 The X-53 F/A-18 was modified to allow two leading edge control surfaces to work in concert with its two trailing edge surfaces to control wing aeroelastic twist and provide excellent high speed rolling performance.AAW developed from the observation that the aeroelasticity can be offset by the deployment of other control surfaces on the wing.In particular, almost all modern aircraft use some form of slat along the wing's leading edge to provide more lift during certain portions of flight.