To conserve angular momentum, an opposite circulation fluid loop forms around the airfoil.
: The air sticks to the wing surface due to friction (the no-slip condition). This creates a boundary layer that prevents the flow from separating prematurely, allowing the air to smoothly follow the upper curve of the wing and leave the trailing edge cleanly (the Kutta condition). The Real Physics Chain of Lift Generation
Doug McLean's book, Understanding Aerodynamics: Arguing from the Real Physics