Abstract: A tailgate aileron system is disclosed, in which a tailgate of a pick-up truck, dump truck or portable roll-off contained has a rectangular opening within which is installed an aileron capable of manual or powered operation. The aileron pivots on an axle disposed horizontally through the central axis of the aileron. The aileron axle registers with bushings disposed in the sides of the rectangular opening of the tailgate. One end of the axle protrudes beyond the side of the rectangular opening and conjoins with a means for operating the aileron. A manual means for operating the aileron is comprised of a positioning handle mounted orthogonal to the axle, which is rotated by hand and is fixed in a desired attitude by an index pin which registers with one of a plurality of indices on the positioning handle. A powered means for operating the aileron is comprised of an electric motor which turns the aileron through a system of gears.