The difference in air pressure which is created by the molecules in air help to move kite up into the air.
Explanation:
When air moves faster, pressure of air becomes less. Air moves at a faster speed above the kite than below it and so its pressure is less on top of kite. The air pressure below kite is less. This difference in pressure results in uplifting of kite. Molecules of air with high pressure exerts more force on kite from bottom and thus pushing it up in air.
The greater is the difference between air pressure above kite and air pressure below kite, greater is the amount of force exerted on kite and hence, it reaches a greater height.
