The wind creates a region of rising air directly above the slope, which may extend some distance upwards and outwards from its face because the airflow follows the upward contour of the hill. However, at near vertical cliffs, there is usually an area of turbulence with descending air near the base of the cliff. Downwind of the hill, lee waves can form; these are also used by glider pilots to gain height, but this should not be confused with slope lift.