The upward force acting on the wings of an airplane in flight is called lift. Lift is generated due to the difference in air pressure between the upper and lower surfaces of the wings. The shape of the wings, known as an airfoil, causes the air to flow faster over the top surface than the bottom surface. This difference in airspeed creates a pressure difference, with lower pressure above the wing and higher pressure below it. The resulting pressure difference generates an upward force known as lift, propelling the airplane into the air.