A method of producing at least part of an aircraft aft fuselage, the at least part of the aft fuselage being for attachment to at least part of an aircraft fore section, the method comprising: providing an initial structure, the initial structure being part of the at least part of the aircraft aft fuselage to be produced; providing a reference structure representative of the at least part of the aircraft fore section; positioning the initial structure with respect to the reference structure such that the position and orientation of the initial structure relative to the reference structure is the same as the position and orientation relative to the at least part of the aircraft fore section that the initial structure would have if the at least part of the aircraft aft fuselage was attached to the at least part of the aircraft fore section; measuring a plurality of points on a surface of the reference structure; using the measurements of the surface of the reference structure, determining a datum; specifying a surface, the surface being a desired inner mould line for the at least part of the aircraft aft fuselage; applying, to an outer surface of the initial structure, one or more layers of material; and after the one or more layers of material have been applied to the initial structure, machining, by controlling a cutting device with respect to the datum, the layers of material such that the position and orientation of the outer surface of the layers of material with respect to the reference structure is the same as the position and orientation with respect to the at least part of the aircraft fore section that the specified surface would have if the at least part of the aircraft aft fuselage was attached to the at least part of an aircraft aft fuselage. providing an initial structure, the initial structure being part of the at least part of the aircraft aft fuselage to be produced; providing a reference structure representative of the at least part of the aircraft fore section; positioning the initial structure with respect to the reference structure such that the position and orientation of the initial structure relative to the reference structure is the same as the position and orientation relative to the at least part of the aircraft fore section that the initial structure would have if the at least part of the aircraft aft fuselage was attached to the at least part of the aircraft fore section; measuring a plurality of points on a surface of the reference structure; using the measurements of the surface of the reference structure, determining a datum; specifying a surface, the surface being a desired inner mould line for the at least part of the aircraft aft fuselage; applying, to an outer surface of the initial structure, one or more layers of material; and after the one or more layers of material have been applied to the initial structure, machining, by controlling a cutting device with respect to the datum, the layers of material such that the position and orientation of the outer surface of the layers of material with respect to the reference structure is the same as the position and orientation with respect to the at least part of the aircraft fore section that the specified surface would have if the at least part of the aircraft aft fuselage was attached to the at least part of an aircraft aft fuselage.