Which flight control surface primarily affects the aircraft's lateral movements?

The aileron is the flight control surface that primarily affects the aircraft's lateral movements. It is located on the outer sections of each wing and operates by moving up or down in opposition to each other. When one aileron is deflected upwards, the other is deflected downwards, which creates a difference in lift between the two wings. This differential lift causes the aircraft to roll, allowing it to bank left or right. This rolling motion is crucial for maneuvering during flight, particularly during turns.

Other control surfaces serve different functions; for instance, elevators primarily control pitch, while rudders are used to manage yaw, stabilizing the aircraft's direction. Flaps are important for increasing lift during takeoff and landing but do not significantly contribute to lateral control. Understanding these roles solidifies why the aileron is recognized as the key surface for lateral movement.