A fan nacelle for an aircraft gas turbine engine. The nacelle includes an aft nacelle portion including a radially outer surface and a radially inner surface, the radially outer and inner surfaces defining an internal cavity therebetween. The nacelle further includes an aft nacelle segment translatable along a translation vector having an axial component, wherein the aft nacelle segment is configured to translate between a forward deployed position in which the nacelle defines a first primary fan nozzle exit area (A1) and a clean position in which the nacelle defines a second primary fan nozzle exit area (A2) less than the first primary fan nozzle exit area A1, wherein in the forward deployed position, the aft nacelle segment is at least partly located within the internal cavity.