RE: Why do people say the top of the wing causes the plane to fly?
Well its not really true.
The curved top wing is designed to eliminate stall upon high angles of attack and slower than efficient speed over the wing.
There is some downward redirection of airflow going on here but at say 5 degrees of downward flow, this doesnt make the plane fly.
It's not the low pressure on top of the wing that makes a plane fly, it's the high pressure on the bottom of the wing that makes it fly.