Flight is the process by which an object moves, through an atmosphere (the air in the case of earth) or beyond it (as in the case of spaceflight) without direct support from any surface. This can be achieved by generating aerodynamic lift, propulsive thrust, aerostatically using buoyancy, or by ballistic movement. Many things fly, from natural aviators such as birds, bats and insects to human inventions such as missiles, aircraft such as airplanes, helicopters and balloons, to rockets such as spacecraft.