An aircraft control structure (108, 200) includes first (212) and second outer surfaces (214) joined to a side wall (212). Stiffening webs (230, 234, 238) extends between the first (212) and second outer surfaces (214), each stiffening web at least partially surrounding an associated aperture (218, 220, 222) formed in either the first or second outer surface and defining a stiffening recess (248). Skin plates (260, 262, 264) are sized to extend over an associated stiffening recess and are shaped to conform to an associated aperture (218, 220, 222). Each skin plate is joined to an associated stiffening web by a friction stir welded seam (300, 302, 304).