Which is the upward force acting on the wing of an airplane in flight?

The upward force acting on the wing of an airplane in flight is called lift.
This force is created by the difference in air pressure between the top and the bottom of the wing, and it is due to the shape of the wing. In fact, due to the shape of the wing, the air flowing on top of the wing is faster than the air flowing on bottom of it. Due to Bernoulli's equation:

where p is the pressure,  the air density and v the speed of the air, we see that if the speed increases, the pressure decreases, and vice-versa. For this reason, the pressure on the lower surface of the wing is greater than the pressure on the upper surface, and this generates the lift, the force acting upward.