What is the primary purpose of using winglets on an aircraft's wingtips?

The primary purpose of using winglets on an aircraft's wingtips is to increase the lift-to-drag ratio. Winglets help to minimize drag caused by wingtip vortices, which are spiraling patterns of rotating air left behind a wing as it generates lift. These vortices lead to induced drag, which can significantly reduce the efficiency of the aircraft. By adding winglets, the airflow is more efficiently managed, reducing these vortices and thus decreasing drag. This improvement in efficiency allows the aircraft to maintain lift with less power, effectively enhancing overall performance and allowing for better fuel efficiency as a secondary benefit. This design feature contributes to more streamlined airflow over the wing, optimizing the aerodynamic performance of the aircraft.