Abstract: A flap such as an aileron or a landing flap is operatively secured to the rear edge of an aircraft wing in such a manner that the wing construction itself may be thin in the direction perpendicularly to the central plane of the wing and as compared to the prior art wing structures. For this purpose a coupling plate extending vertically is secured to the bottom of the flap. The coupling plate provides two journal points arranged substantially vertically one above the other. The upper journal point is connected to the wing. The lower journal point is connected to a rocker drive. A drive piston rod is connected through crank levers to rotate the coupling plate in the manner of a four journal drive.