In the context of airspeed indicators, what is 'stalling speed'?

Stalling speed refers to the minimum speed at which an aircraft can maintain level flight. When the aircraft drops below this speed, it loses lift, which can result in a stall. During a stall, the wings are no longer able to generate enough lift due to the angle of attack exceeding the critical threshold. This is a crucial parameter for pilots to understand, as flying below this speed could lead to a loss of control and potentially dangerous situations.

Other options focus on different aspects of flight performance. The safest landing speed is typically higher than stalling speed, and maximum altitude is not directly tied to stalling speed as it depends on various other factors, including weight and atmospheric conditions. Average cruising speed is also different from stalling speed since cruising speeds are generally much higher, designed for efficiency during flight rather than the bare minimum required to sustain lift.