Many high-wing airplanes have external braces, or wing
struts, which transmit the flight and landing loads through
the struts to the main fuselage structure. Since the wing struts
are usually attached approximately halfway out on the wing,
this type of wing structure is called semi-cantilever. A few
high-wing and most low-wing airplanes have a full cantilever
wing designed to carry the loads without external struts.

The principal structural parts of the wing are spars, ribs,
and stringers. [Figure 2-7] These are reinforced by trusses,
I-beams, tubing, or other devices, including the skin. The
wing ribs determine the shape and thickness of the wing

(airfoil). In most modern airplanes, the fuel tanks either are
an integral part of the wing's structure, or consist of flexible
containers mounted inside of the wing.

Attached to the rear or trailing edges of the wings are two
types of control surfaces referred to as ailerons and flaps
Ailerons extend from about the midpoint of each wing
outward toward the tip, and move in opposite directions to
create aerodynamic forces that cause the airplane to roll.
Flaps extend outward from the fuselage to near the midpoint
of each wing. The flaps are normally flush with the wing's
surface during cruising flight When extended, the flaps move
simultaneously downward to increase the lifting force of the
wing for takeoffs and landings. [Figure 2-8]