Aircraft

An aircraft is a vehicle which is able to fly by being supported by the air, or in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift (as with balloons, blimps and dirigibles) or by using the dynamic lift of an airfoil (as with vehicles that plane the air with wings in a straight manner, such as airplanes and gliders, or vehicles that generate lift with wings in a rotary manner, such as helicopters or gyrocopters).
Objects which fly, but are not supported by the air, such as most rockets and missiles, are not considered aircraft. These types of vehicles use rocket thrust instead of lift as the primary means of overcoming the force of gravity. Other objects which fly by using aerodynamic lift, such as kites and Frisbees, can only be considered aircraft if they are used as vehicles.[citation needed] Ballistic flying objects such as arrows, bullets and artillery are not aircraft, because they do not use the air as their means for countering the force of gravity. Parachutes are not usually considered to be aircraft (although they may be) because they have a lift-to-drag ratio well below one, and thus fly extremely poorly. However, parasails and paragliders possess a much high lift-to-drag ratio and are nearly always considered aircraft. For an even more specialized case a rocket with wings such as the X-1, X-15 or the EZ-Rocket does typically function as an aircraft when it is flying in its rocket mode using aerodynamic lift, but would not if flown as a spacecraft outside of the atmosphere, and where it is therefore not supported by the air. So it is possible for the same vehicle to either count or not count as an aircraft depending upon its usage.
The human activity which surrounds aircraft is called aviation. Manned aircraft are flown by an onboard pilot. Unmanned vehicles are often called drones, remotely piloted vehicles (RPV) or unmanned aerial vehicles (UAV).