The weight of an aero plane flying in air is balanced by

Options :

1. Upthrust of the air which will be equal to the weight of the air having the same volume as the plane

2. Force due to the pressure difference between the upper and lower surfaces of the wings, created by different air speeds on the surface

3. Vertical component of the thrust created by air currents striking the lower surface of the wings

4. Force due to the reaction of gases ejected by the revolving propeller