If there is a gravity on earth how airplane fly on air?

Because there is a upward force on the wing greater then the gravitational force downward.

Good question. Here's how it works. An airblane (or bird) wing is curved on top and flat on the bottom. When the wing moves through the air, this means the air has more disance to travel over the wing. There's a physical principle (Carnot's Law) that tells us what happens in such situations: the air will move faster--but the pressure will drop. The result is that the pressure on the bottom of the wing is higher thn on the top--producing lift. If the pressure difference iis fairly high--sayabout 5%-thats about 50 lbs of force on every square foot of the planes wings--pushing directly upward. That's a lot of force--and that's what lifts a plane off the ground and enables it to fly. Of course you need to have a good engine (or strong wings if you''re a bird) to produce enough thrust get moving fast enough to make the air flow and lift strong enough--especially since they also have to overcome air resistance (called drag) as well. That's why aircraft need long runways--so they can get up enough speed. To sum this up--the physical law that describes how airplanes and birds fly is: When thrust plus lift exceed weight plus drag, the plane (bird) will fly.

It's pretty easy once they get up in the air, because that has it's own "Specific gravity" which is a lot lower than the "specific gravity" of the earth.

The trick is getting them big 747s to take a running leap into the sky and flap their wings enough to get away from the specific gravity of the dust they kick up.

It takes a lot of horses packed into them engines to do that.

They suck in air to push them off the ground, ya know like a roocket gets pushed up in space when fire if blowed out the bottom well airplans use air to push up.

The shape of an airplanes wing creates lift.

they have wings?? thats a good question

but i suppose the gravity levels of earth aren't that high

There is still gravity until you reach the exosphere.

because gravity only has a certain power, a plane is powerful enough to overcome this, even we are momentarily when we jump i suppose.

The same way birds fly. & they have been doing it longer then man.

Call the scientist! there is no gavity!

http://www.nasa.gov/audience/forkids/home/F_How_Do...