Abstract: According to the present invention, there is provided a jet engine comprising a cowl, an exhaust nozzle at the rear of the engine, a plurality of vanes that extend substantially circumferentially around the cowl of the engine in the region of the exhaust nozzle, means to support the vanes on the cowl so that the vanes can be moved between a retracted position in which they lie close to the cowl and an extended position in which they are spaced apart from the cowl so that, together with the cowl, the extended vanes define a substantially annular duct having an inlet and an outlet, one or more nozzles beneath each vane for directing high pressue air into the duct in a direction towards the rear of the engine, means for feeding high pressure air from the engine to the nozzles and an actuator arrangement for moving the vanes between the extended and retracted positions.