Therefore, if the airfoil deflects the air down, the resulting opposite reaction is an upward push. Deflection is an important source of lift. There are some planes that do not have cambered wings. Their wings are flat and are designed to fly at very high speeds. These planes get lift only by deflection.
Planes flying upside down, even with cambered wings, can deflect enough air to get lift.
The amount of lift a wing can produce is governed by several factors. The weight of the object to be flown. The size of the under surface of the wing. The larger the wing the more lift produced. Another way to increase the lift is to change the angle of the wing as it faces the air.