What is the primary force that opposes weight and keeps an airplane in the air?

Lift is the primary force that opposes weight and sustains an airplane in flight. It is generated by the wings of the aircraft as air moves over and under them. The shape of the wings (specifically, an airfoil shape) causes the air pressure on top of the wing to be lower than the pressure on the bottom, creating an upward force. This upward force must exceed the gravitational pull (weight) acting on the airplane for it to ascend and stay airborne.

In the context of flight, while drag refers to the resistance an aircraft faces as it moves through the air and turbulence involves chaotic air movement that can affect flight stability, neither of these forces counteracts weight effectively. The center of gravity, on the other hand, is a pivotal point where an airplane's weight is evenly distributed, but it doesn't itself act as a force to keep the airplane aloft. Therefore, lift is the fundamental aerodynamic force necessary for maintaining altitude in an aircraft.