how do an aircraft operate?

Answer 1

There are four forces working on an airplane while it is flying, thrust, drag, lift, and gravity. Thrust is provided by the engine, either though a propeller or direct thrust as in a jet.
Drag opposes thrust and when a plane is at a constant speed balances it. Drag is what you feel if you stick your hand out of the window of a moving car. It is the air resisting movement though it.
Gravity I'm sure you know. It's what keeps out feet on the ground.
Lift is caused by two things on an airplane. As mentioned Bernoulli's principle causes some, usually most of the lift. The shape of the wing, and sometimes other parts of the plane causes the air to move faster over the top of the surface causing it to become less dense. This causes the denser air on the bottom to "push" up on the surface and give it lift. Deflection of the air also causes lift. A perfectly flat wing can create a large amount of lift when it is angled right. The drawback to using a flat surface is that it also causes a LOT of drag for the lift it creates.

A supersonic plane flies exactly the same as a subsonic plane, all the principles are the same. Jets usually have poor glide ratios because they are designed for minimum drag at supersonic speeds. This design leads to high wing loading (pounds of airplane per square foot of wing area) and shapes that are not efficient at lower speeds.

A glider, or a jet that has lost power, trades altatude for speed, in effect always going down hill. The more drag a plane has the faster it looses altutude to keep its speed.

Answer 2

Subsonic aircraft work by Bournelli's principle: the air flowing over the longer top surface of the wing flows farther than the bottom, thus causing lift, or increasing the coefficient of lift, cL.

Supersonic aircraft work by using the wings as steering and stabilizers; basically the powerful engine makes the fusilage a missle. Most jets, especially military jets, do not glide well.

Answer 3

Wind_rider provides a pretty good answer. The physics behind flight can be quite complicated, although very eligant. As far as a basic answer goes he is correct.