A propulsion unit for an aircraft

This invention relates to a propulsive unit (10) for an aircraft, comprising: a nacelle (12) which defines a duct (20) for channelling an airflow when in use and which provides an outwardly facing surface (14) of the propulsive unit (10), the outwardly facing surface (14) having an aerodynamic shape; a fan unit (16) for accelerating the airflow within the duct (20) when in use; wherein the duct (20) has an inlet (26) and an outlet (28) and the nacelle (12) is operable to adjust the either or both of the area of the inlet (26) and outlet (28) whilst substantially retaining the aerodynamic shape of the outwardly facing surface.