KISS. Newton's third law. To every action is an equal and opposite reaction.
That is the answer in a nutshell.
Aircraft fly because the upward force opposite to their weight is equal.
The way aircraft produce such opposing force is by deflecting air downwards. Now whether it is by aerofoils , bernoulli, coanda, flat plates or pure chance, it makes no odds. It is simply the downward deflection of the air that causes an opposite force upward on the aircraft.
Last edited by indiscipline_girl; 24th Dec 2008 at 10:30.
Reason: Can't spell bernoulli but then who can?