Air flight is the use of a powered flying vehicle (airplanes, jet aircraft, helicopters, hot air balloons, blimps, gliders) to travel from one point to another over a large distance. This is an alternative to other forms of transport such as cars or trains, and it can be a much quicker way of getting around. Modern airplanes use very little fuel per person and mile when fully loaded, and the process of boarding and deplaning is usually a lot quicker than it would be with other modes of transportation.

All creatures and machines capable of flight must generate lift to overcome the drag that opposes it. This is accomplished by arranging a structure that is lighter than the air, such as an airplane wing, in such a way as to provide the greatest possible ratio of lift to weight. Depending on their specific design, different wings may be more or less efficient in creating lift, and this is affected by the shape of the wing and the angle at which it is angled with respect to the wind.

A fixed-wing plane generates forward thrust by accelerating the air it moves through. This can be done through a rotating fan pushing air out of the back of the engine, through the spinning blades of a propeller, or by ejecting hot gases from an internal combustion engine. Reverse thrust can be produced by reversing the pitch of variable-pitch propellers or using a thrust reverser on jet engines.

The aerodynamic forces that control the stability and attitude of a plane in flight are the tail surfaces, movable aerodynamic devices (including rudders and ailerons) and, in most cases, engine thrust vectoring. A plane’s wing configuration also affects the way in which it flies: a wing with an elliptical “positive dihedral” angle creates greater lift and is more aerodynamically desirable than a rectangular wing of equal area.

Those forces which keep a plane aloft require considerable energy, so all vehicles capable of flight must be designed with a high power-to-weight ratio. This is reflected in the fact that most commercial aircraft have wings of fairly large area for their overall mass, and in the fact that most commercial aircraft use powerful engines to achieve high speeds.

Planes are often the fastest and most convenient way to get from one place to another, and they can also be used to reach remote locations which are not accessible by road or rail. They also offer the possibility of travelling long distances in a very short period of time, especially when compared to taking buses or trains, and they can be much more comfortable than driving or sitting in a car. This convenience comes at a cost, though, and planes are notoriously expensive to operate if they are full of passengers. For this reason, it is best to book tickets in advance. Typically, the cheapest days to fly are on Thursdays and Fridays, when many people are leaving for the weekend or returning from work.