Abstract: A gas turbine engine terminates at its rear in a jet pipe (14) having a fixed area nozzle (15). The engine is provided with one or more target type deflector doors (18) which in a first position constitute a rearward extension of the jet pipe (14) and define an effective exhaust nozzle (19), downstream of the nozzle (15) of the jet pipe 18, which is of smaller area than that of the jet pipe. The door, or doors 18, are movable from the first position to a second position where the nozzle 15 of the jet pipe 14 is exposed and constitutes the effective exhaust nozzle of the engine. In the second position the door, or doors 18, lie predominantly transverse to the length of the jet pipe 14 to redirect the hot gas efflux from the jet pipe 14 and reduce the forward thrust produced by the engine.