What happens to lift if the weight of an airplane increases during flight?

If the weight of an airplane increases during flight, lift must increase to maintain level flight. This principle is based on the basic aerodynamic concept that an aircraft must generate enough lift to counteract its weight in order to maintain altitude.

When an airplane’s weight increases—whether due to fuel burn, cargo, or other factors—the lift generated by the wings at a given speed and angle of attack will not be sufficient to hold the aircraft aloft if it remains unchanged. Therefore, to sustain level flight, the aircraft needs to produce more lift by increasing speed, adjusting the angle of attack, or a combination of both. This ensures that the aerodynamic lift counterbalances the increased weight, thus allowing the aircraft to fly straight and level.

This concept is crucial for pilots to understand, as managing the lift-to-weight relationship directly impacts flight safety and performance.