Abstract: A STOL aircraft has high mounted left and right wings, each of which defines an upper airfoil surface. A mixed flow turbofan engine is mounted on each wing such that the exhaust nozzle of the engine is positioned adjacent but rearwardly of the leading edge of the wing and such that in a cruise mode of operation the exhaust stream exits from the nozzle substantially chordwise across the airfoil surface. A set of trailing edge flaps is located on each wing aft of the exhaust nozzle. When the flaps are extended, spanwise slots are formed by separation of flap segments from the wing and from each other. The flaps include closure apparatus for closing off the slots during STOL operation so that the flaps, closure apparatus and rear portion of the upper airfoil surface form a smooth downwardly curved surface aft of the engine. The slot closure devices can be retracted to allow the flaps to operate as conventional aerodynamic slotted flaps in case of engine failure.