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We Aren’t Built to Fly

We Just Aren’t Built to Fly

Birds inspired our first attempts to fly, but our progress was limited until we learned that we could not fly like them. Thanks to their light weight, great strength, and complex biological design, birds and other flying creatures can use their wings to create both lift and thrust, as well as to maintain control.

Drawing, sheet 2 of 5, U.S. Patent No. 398984, issued March, 5, 1889, for Reuben J. Spalding's Flying Machine. Consisting of wings and a tail attached to a man, the man-powered ornithopter device was designed to make its wearer look (and fly like) a bird.
Credit: National Air and Space Museum, Smithsonian Institution, Archives Reference No.: 74-741

In order to fly:

  • We need to overcome our own weight—that is, the force of gravity.
  • To overcome gravity, we need to create an upward force called lift.
  • To create lift, we need to generate thrust for forward motion.
  • To keep moving, we need to overcome the resistance of the air—a force called drag.

But using only our muscles, we can’t get off the ground very high or very far for very long. So instead, we’ve created machines to do what we alone cannot. We separated the functions of lift and thrust, using wings to produce one and engines to produce the other.

Though we still cannot fly like birds, we can now fly with them.

Ask an Explainer


What is an ornithopter?


An ornithopter is a birdlike machine that generates lift and thrust by flapping its wings. An ornithopter doesn't need to have feathers, though. The word "ornithopter" comes from the Greek words for "bird" and "wing." The first ornithopters capable of flight were toys built in the late 19th century in France. ... more

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Did You Know?

Humans have wanted to fly like birds for thousands of years. The ancient Greeks made-up the story of Icarus and Daedalus, who made wings from bird feathers and wax. And in the 15th Century, Leonardo da Vinci designed a human powered, winged machine known as an ornithopter.

Hands-On Experiments

Pop Quiz

What forces affect birds and insects in flight?

A) Thrust and lift
B) Thrust, drag, weight and lift
C) Weight and drag
D) Drag, weight and lift

The basic forces that act upon aircraft and spacecraft – lift, weight, drag and thrust – are the same forces that govern the flight of birds and insects.