Aircraft wing vortices. Spirals of air flowing off the upper surface of an airplane wing during takeoff. These vortices are formed due to the difference in pressure between the upper and lower surfaces of the wing. As streamlines of air flow above and below the aerofoil they travel at different speeds. This results in lower pressure above the wing than below it, which in turn results in a net force or 'lift' upwards. The shape of the aerofoil influences the way in which air flows over it and hence the amount of lift that can be generated.