A gas turbine engine (30) comprising a rear cowl (38) defining an exhaust aperture (40) and a motive system. The rear cowl (38) comprises at least one panel (42) and the motive system is operable to selectively move the panel (42) between deployed and stowed configurations by rotation of the panel (42) about an axis substantially parallel to the main rotational axis of the engine (30). This alters the area of the exhaust aperture (40).