How does a aircraft fly?

Answer 1

Airplanes have wings which are shaped as a stretched out D on it's back.

This shape enables a force called lift to occur. When air moves past the wing, it creates lower presssure on the top of the wing and higher pressure below the wing which creates the force of lift.

Read this for more information :

http://web.mit.edu/16.00/www/aec/flight.html
The force on the plane (jet perhaps) sends it forward and the design of the wings sends air downwards, thus forcing the aeroplane into the air.

Answer 2

An aircraft flys by using a combination of wings and an engine. The faster air travels, the lower the pressure (simple experiment - place a straw in a glass of water and blow over the top of it, see how the water is sucked up?). If we look at the shape of a wing we can see that the top side is slightly longer than the straight bottom side. This means the air has to flow over the top faster to cover the distance. As mentioned, faster air means a lower pressure. This low pressure causes a suction effect or "lift" which put very very simply causes the aircraft to stay in the air or "fly". To create the process of "air flow over the wings" aircraft use a range of engines to pull it forwards thus causing air to pass over the wings. All explained by the: "Bernoulli Principle".