The angle of incidence is the angle formed by the wing chord line and the aircraft longitudinal axis. The wing chord line extends from the leading edge of the wing to the trailing edge of the wing. The longitudinal axis is an imaginary line that extends from the nose of the aircraft to the tail.
The angle of incidence is measured by the angle at which the wing is attached to the fuselage and in general, the angle of incidence is fixed and cannot be changed by the pilot.
The angle of incidence is usually set at a small positive angle in order to allow the fuselage to maintain level during normal cruising flight. The angle of incidence varies on different aircraft. Angle of incidence should not be confused with angle of attack.