About 100 years ago, man invented the airplane. Before that, only birds, insects, and bats knew how to fly. Millions of years ago, there were some dinosaurs that could fly, but they became extinct long before man lived on earth.

There are two kinds of flight in the natural world: gliding flight and true flight. When something glides, it floats through the air without using power. True flight requires energy to move wings up and down.

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Hear what astronauts have to say about staying drug-free.
Last modified: Mon Jul 7 11:10:34 PDT 1997