Flight is the process of flying: either movement through the air by aerodynamically generating lift or
aerostatically using buoyancy, or movement beyond Earth's atmosphere by spacecraft.
Pterosaurs were a group of flying vertebrates contemporaneous with the dinosaurs.
Bats are the only mammals capable of true flight. However, there are several gliding mammals which are able to glide from tree to tree using fleshy membranes between their limbs: some can travel hundreds of metres in this way with very little loss of height. Flying tree frogs use greatly enlarged webbed feet for a similar purpose, and there are flying lizards which employ their unusually wide, flattened rib-cages to the same end. Flying snakes also use a flattened rib-cage to fly, with a back and forth motion much the same as used on the ground.
Flying fish can glide using enlarged wing-like fins, and have been observed soaring for hundreds of metres using the updraft on the leading edges of waves. It is thought that they evolved this ability to help them escape from underwater predators.
Most birds fly, with some exceptions. The largest birds, the ostrich and the emu, are earthbound, as were the now-extinct dodos, while the non-flying penguins have adapted their wings for use under water. Most small flightless birds are native to small islands, and lead a lifestyle where flight confers little advantage.
Among the millions of species of insects, many do not fly.
Among living animals that fly, the wandering albatross has the greatest wingspan, up to 3.5 metres (11.5 feet), and the trumpeter swan perhaps the greatest weight, 17 kilograms (38 pounds).
