Anything that's contagious and dangerous. If you have ebola, they'd prefer you stay home.
A paper airplane cannot fly without a wing.
Planes cannot fly backwards.
Can you fly on airplane with pericarditis
People fly by traveling in airplanes, which use engines to generate enough thrust to overcome gravity and lift the aircraft into the air. The shape of the wings on the airplane create lift, allowing it to stay airborne. By controlling the speed and angle of the airplane, pilots are able to navigate through the sky.
An airplane, by definition, flies in the air, it does not fly in outer space where there is no air. So an airplane cannot fly from Earth to Mars. That requires a spaceship. With current technology, a spaceship might reach Mars in about a year. It's a long trip.
It is an illness some people get while flying in an airplane.
They are an important part of the aircraft that makes it fly. There are many other parts without which the airplane cannot fly.
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The wind pushes the airplane helping it to stay in the air and fly.
Igor Sikorsky was the first person to fly in an airplane, in his 1913 airplane called "The Grand." The Wrights were the first people to fly an airplane, but you fly ON a Wright Flyer--it's very open. Sikorsky invented the enclosed cockpit.
An airplane produces enogh lift to fly with weight. Cargo planes are designed to do that.