To be able to extend the flight envelope of modern fighter aircraft to high angles of attack , it is necessary to be able to control and guide the movement of the aircraft under very severe conditions characterised by extensive air separations on the fuselage and wings.

Such movements are necessary to be able to make difficult manoeuvres to combat a threat or to go into firing position during an air combat. These flight conditions require special aerodynamic performance capabilities involving new types of control surfaces and suitable flight models. These models are evaluated under operational conditions and are currently used for air combat simulations.