If you turn the aircraft upside down, the air flowing over the upper (formerly lower) surface of the wing will still flow faster. This can be acheived by most airfoils (including a flat plate) by adjusting the angle of attack properly (point the nose of the aircraft somewhat upwards). If memory serves me right, approximately 2/3 of the lift is generated by suction over the upper surface (air flowing faster than ambient airflow) and 1/3 by overpressure (air moving slower than ambient airflow) over the lower surface. This again varies with the airfoil in use.
Biting the hand that feeds IT
