What aerodynamic factor causes wingtip vortices?

Wingtip vortices are caused primarily by the phenomenon of lift generation on the wings of an aircraft. When a wing generates lift, the pressure on the upper surface of the wing is lower than that on the lower surface. This pressure difference causes the air from below the wing to flow around the wingtip and into the relatively lower pressure area above the wing. As a result, this movement of air creates a swirling motion, leading to the formation of vortices that spiral downward off the wingtips.

Understanding this principle is crucial for pilots, as wingtip vortices can pose hazards to following aircraft, particularly during takeoff and landing phases, where wake turbulence can impact performance and safety. The correct answer highlights the aerodynamic relationship between lift and vortex formation, which is the root cause of wingtip vortices.