An aircraft comprising a fuselage, a sail wing appended to the fuselage, the sail wing having a sail wing root chord length, and wherein the sail wing includes a sail wing leading edge spar, a sail wing membrane attached to the sail wing leading edge spar, and a sail wing trailing edge wire located at a trailing edge of the sail wing membrane, the aircraft further comprising a wing surface extension, located aft and at an inboard area of the sail wing trailing edge wire, the wing surface extension having a wing surface extension root chord length, and wherein the wing surface extension includes a wing surface extension membrane attached to the sail wing trailing edge wire, and a wing surface extension trailing edge, and wherein the wing surface extension trailing edge is reflexed such that the wing surface extension trailing edge is positioned upwards at a first angle with respect to a plane formed along a centerline of the aircraft and along the lower surfaces of the sail wing. The wing surface extension is further configured to affect a reduced nose-up pitching moment, and to produce a more even coefficient of lift along the wing of the aircraft.