What happens to an aircraft's stall speed as its weight decreases?

As the weight of an aircraft decreases, its stall speed also decreases. This relationship is primarily because stall speed is influenced by the aircraft's weight as it affects the amount of lift required to maintain level flight.

Stall speed is defined as the minimum speed at which an aircraft can maintain controlled flight. This speed increases with weight because the aircraft must generate more lift to counteract the increased gravitational forces acting on it. Conversely, when the aircraft's weight is reduced—such as when fuel is burned off or cargo is unloaded—the necessary lift to prevent a stall also decreases. As a result, the stall speed decreases proportionately.

Other options describe incorrect scenarios: an increase in stall speed typically occurs with an increase in weight, not a decrease. The stall speed does not remain constant as it is directly affected by weight changes. While drag does increase during maneuvers like slow flight, the fundamental relationship regarding weight and stall speed remains the primary focus here. Thus, the correct answer reflects the fundamental aerodynamic principles governing stall characteristics related to weight changes.