What causes an aircraft to turn during flight?

An aircraft turns during flight primarily due to the horizontal component of lift. When an aircraft is banked or tilted during a turn, the lift vector does not act directly upward; instead, it is inclined at an angle relative to the vertical. This inclination results in two components: a vertical component that supports the weight of the aircraft and a horizontal component that generates the necessary force to change the aircraft's direction.

This horizontal component of lift acts towards the center of the turn, effectively creating a centripetal force that allows the aircraft to follow a curved path. For successful turns, the pilot manages the bank angle to ensure that enough lift is directed horizontally to maintain the turn radius and altitude. Hence, the horizontal component of lift is essential for maneuvering the aircraft in flight.