According to Wikipedia lift in an aircraft is due to an area of low pressure formed above the wings of an aircraft due to the fast moving air there. So why exactly is an area of low pressure created due to fast moving air?
[Physics] Why does moving air have low pressure
aerodynamicsaircraftbernoulli-equationfluid dynamicsnavier-stokes;
Related Solutions
First thing, that's a common misconception that the plane flies due to the Bernoulli effect.
See the these questions: What really allows airplanes to fly? Why does the air flow faster over the top of an airfoil? for the correct explanation.
Assuming that the bernoulli effect does explain flight, the answer to your question is:
Pressure of a fluid is force exerted by a fluid on a unit area of a neighboring body (the force exists inside the fluid as well, but it is balanced). So, if there is more pressure underneath, the upward force is greater (area if top and bottom of wings are approximately the same)
If the upward force is greater, the net force due to pressure is upwards. This force is called 'lift', and it balances gravity, helping the plane fly.
Read http://enwp.org/Pressure for more info.
The simple answer is that a wing moves through the air generally at a non-zero angle of attack. The air flow below the wing sort of impacts the wing surface, compressing and slowing down as it is deflected.
Best Answer
It's all about conservation of momentum, $F=ma$. Fluid can only change velocity by experiencing a force, and the only force it can feel is a pressure difference. So if there's a velocity difference, there's a pressure difference, and vice-versa (neglecting other things, like gravity). Read this beautiful exposition.