A method of producing an assembly tool for assembling at least part of an aircraft aft fuselage, the at least part of an aircraft aft fuselage comprising one or more airframe components (8, 10, 12), the at least part of an aircraft aft fuselage being for attachment to at least part of an aircraft fore section, the method comprising: for each component (8, 10, 12), determining a position and orientation relative to the at least part of the aircraft fore section that that component (8, 10, 12) would have if the at least part of the aircraft aft fuselage was attached to the at least part of the aircraft fore section; for each component (8, 10, 12), using the determined position and orientation of that component (8, 10, 12) relative to the at least part of the aircraft fore section, determining one or more positions and orientations relative to the at least part of the aircraft fore section at which that component (8, 10, 12) is to be supported; providing a jig frame; attaching, to the jig frame, a reference structure, wherein the reference structure is a substantially exact replica of at least part of the aircraft fore section to which the at least part of the aircraft aft fuselage is to be attached; providing a plurality of pickup devices (66, 68, 70, 72) each having a receiving element (74, 76, 78, 80) for receiving a component (8, 10, 12) of the at least part of the aircraft aft fuselage; and securing each pickup device (66, 68, 70, 72) to the jig frame such that a position and orientation relative to the reference structure of each receiving element (74, 76, 78, 80) is the same as a respective determined position and orientation relative to the at least part of the aircraft fore section at which a component (8, 10, 12) of the at least part of the aircraft aft fuselage is to be supported. for each component (8, 10, 12), determining a position and orientation relative to the at least part of the aircraft fore section that that component (8, 10, 12) would have if the at least part of the aircraft aft fuselage was attached to the at least part of the aircraft fore section; for each component (8, 10, 12), using the determined position and orientation of that component (8, 10, 12) relative to the at least part of the aircraft fore section, determining one or more positions and orientations relative to the at least part of the aircraft fore section at which that component (8, 10, 12) is to be supported; providing a jig frame; attaching, to the jig frame, a reference structure, wherein the reference structure is a substantially exact replica of at least part of the aircraft fore section to which the at least part of the aircraft aft fuselage is to be attached; providing a plurality of pickup devices (66, 68, 70, 72) each having a receiving element (74, 76, 78, 80) for receiving a component (8, 10, 12) of the at least part of the aircraft aft fuselage; and securing each pickup device (66, 68, 70, 72) to the jig frame such that a position and orientation relative to the reference structure of each receiving element (74, 76, 78, 80) is the same as a respective determined position and orientation relative to the at least part of the aircraft fore section at which a component (8, 10, 12) of the at least part of the aircraft aft fuselage is to be supported.