Aircraft

(PD) Photo: PDPhoto.org
Airplanes are a type of heavier-than-air aircraft.

(PD) Photo: -- Bryan Kennedy
A hot air balloon is a type of lighter-than-air aircraft.

Aircraft are vehicles capable of sustained flight within the Earth's atmosphere.

Vehicles that travel beyond the Earth's atmosphere, normally defined as 100,000 meters altitude, are called spacecraft.

Aircraft remain aloft using on two basic principles: 1) aerodynamically by pushing air downward or 2) aerostatically by using low density gas.

Most aircraft use aerodynamic lift. These include airplanes and helicopters.

Aircraft that use aerostatic lift include balloons and airships.