Aerostructure refers to the individually manufactured sections of an airframe, such as the wings, fuselage, pylons, flight control surfaces, nacelles, thrust reversers, and empennage. Each of these components represent a required piece of the aircraft skeleton, upon which additional equipment may be mounted. For large-scale aircraft, components are often produced separately and gathered at the final assembly line. Manufacturers differ on services offered, as some may preassemble components or complete the final assembly of their product. Aerostructures are essential in the completion of any aircraft, be it fixed-wing or rotorcraft, or intended for commericial, civilian, or military use.