What component is located on the outer portion of the wings and improves fuel efficiency?

Winglets are small vertical fins attached to the tips of an aircraft's wings. Their primary role is to improve aerodynamic efficiency by reducing drag caused by wingtip vortices, which are circular patterns of rotating air left behind by a wing as it generates lift. These vortices create induced drag, which increases fuel consumption. By incorporating winglets, the aircraft experiences a reduction in this drag, leading to improved fuel efficiency and performance during flight.

Additionally, winglets can help enhance an aircraft's stability and control. Their design allows the lift generated by the wings to be used more effectively, which not only conserves fuel but can also extend the range of the aircraft. This is particularly beneficial for airlines looking to reduce operational costs and environmental impact.

In contrast, ailerons are primarily used for lateral control and maneuverability rather than fuel efficiency, while flaps assist in increasing lift at lower speeds but can also increase drag. The nacelle houses the engines and has a more structural function than that of enhancing aerodynamic performance. Therefore, winglets stand out as the component specifically designed to enhance fuel efficiency while maintaining overall flight performance.