[wbeaty]

It's wrong because the force on the lower airfoil surface is far smaller than the total lifting force.

The flow above the airfoil "sticks" to the airfoil. Since the upper flow is being forced downwards by the curved upper surface, it forces the airfoil to move upwards.

What happens if the upper flow doesn't curve downwards? Simple. That's called "stall," and your airplane drops out of the sky. "Stall" is when the upper flow becomes detached, and goes straight back, rather than following the curved upper surface. (The force on the bottom of the airfoil is far too small to keep the plane in the air. Most of the lift is created by the upper surface! That's why "stall" is such a huge deal.)