An airframe or a part thereof 3, for example a skin assembly or a profile such as a structural profile, comprises: a wall W having an aperture A therethrough, wherein the wall W provides a frame F surrounding, at least in part, the aperture A; a panel P conforming with the aperture A; and wherein the airframe or the part 3 thereof is configurable in: a first configuration, wherein the panel P and the frame F are mutually spaced apart; and a second configuration, wherein the panel P is received in the frame F and wherein the frame F resists movement of the panel P in two or three mutually orthogonal directions.