Why aircraft overcomes force of gravity.....and becomes flying..?

Answer 1

They do not! The gravity is always there!
And it pulls the aircraft down.
So, to stay in the air, there must be an other force, pulling the aircraft UP, at least equal to the force of gravity.
This force is made by a combination of the horizontal velocity of the plane, the shape of the wings, the angle of attack of the wings and the air resistance: the force of the "air" BELOW the wing is higher than the force on the top of the wing. The difference is a force pushing the aircraft upward.
If this force is larger than the gravity, the aircraft goes up.
And, hopefully, stays up.

Answer 2

Apart from the reasons explained above, there is an important property of fluids (well in this case, the air) involved in keeping the aircraft stay afloat. That property is known as viscosity and can be explained as resistance of a liquid/fluid to sheer forces (and hence to flow). Every fluid has certain viscosity, for example honey has higher viscosity than water. Likewise air also has certain viscosity.

All the reasons in the above answers explains what happens at the leading edge of the wing. But at the trailing edge of the wing, the air flowing over the top of the wing resists to leave the wing in exactly the way it flowed over the leading edge. The air will try to stick to the surface of the wing, the air behind pushes it forward (backwards with respect to aircraft) thereby creating a slight angle downwards to the horizon while leaving the wingtip. This slight angle also helps the aircraft stay afloat.

Hope this is informative and not confusing. Thanks.

Answer 3

Angle of attack and Bernoulli's principle together can explain the lifting force provided by the wings. The lifting force is great enough to overcome gravity

- Wings are angled upward (trailing edge lower than the leading edge) so they will be deflected upwards.
- Air passing over the airfoil cross section of the wing travels faster than air on the bottom of the wing. Pressure is lower on top than on the bottom so there is an upward force.

Answer 4

They have wings, powerful engines etc. and the science of aerodynamics to go-with. So they can keep themselves flying in the air and overcome gravity.