An aileron is a movable FLAP on the trailing edge of an aircraft's WING that is used to control the roll of the aircraft. It is typically found on the outboard section of each WING and is operated by the pilot to increase or decrease the lift on one side of the aircraft, allowing it to roll in the desired direction. The term 'aileron' is derived from the French word for 'little WING'. The crossword solutions for the term 'aileron' are 'FLAP' (4 letters) and 'WING' (4 letters).