An airfoil is a curved surface, such as the wing of an airplane, designed to create lift when air passes over it. The three crossword solutions for the term airfoil are FIN (3 letters), AILERON (7 letters), and FLAP (4 letters). The FIN is a vertical stabilizer located at the back of the airfoil that helps to keep the aircraft stable in flight. The AILERON is a hinged FLAP on the trailing edge of each wing that controls the roll of the aircraft. The FLAP is a hinged section of the airfoil that can be extended downward to increase lift and drag. Finally, the RUDDER is a hinged section of the FIN that controls the yaw of the aircraft.