control surface

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A movable airfoil, especially a rudder, aileron, or elevator, used to control or guide an aircraft, guided missile, or rocket.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun aeronautics A moveable surface attached to a machine such as an aircraft or submarine that can be used to control the machine's motion in roll, pitch or yaw.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a device that provides reactive force when in motion relative to the surrounding air; can lift or control a plane in flight