method for manufacturing an airplane wing comprising:providing a lower wing cover and an upper wing cover,providing a wing spar comprising a first end portion and a second end portion, each of the first end portion and the second end portion respectively comprising a front flange and a rear flange,butt welding the front flange and the rear flange of the first end portion of the wing spar to the lower wing cover; such that the welded first end portion of the wing spar comprises a part of the lower wing cover and forms a butt welded part of an outside of the airplane wing,butt welding the front flange and the rear flange of the second end portion of the wing spar to the upper wing cover, such that the welded second end portion of the wing spar comprises a part of the upper wing cover and forms a butt welded part of the outside of the airplane wing