What occurs to true stall speed as altitude increases?

As altitude increases, the density of the air decreases. True stall speed is defined as the minimum airspeed at which an aircraft can maintain level flight and is influenced by the aircraft's weight and the air density. Although the stall speed relative to air density remains unchanged, the actual true stall speed in terms of indicated airspeed will increase due to the lower air density. This means that even though an aircraft may be at the same angle of attack where it would stall at a lower altitude, the reduced air density requires a higher true airspeed to produce enough lift to maintain level flight.

Indicated stall speed, which is the stall speed indicated on the airspeed indicator, is derived from the dynamic pressure of the air, which is affected by air density. As the aircraft ascends to higher altitudes and the air becomes less dense, the indicated stall speed increases because the airspeed indicator reads based on this lower density environment.

Therefore, true stall speed increases with altitude due to the decreased air density, while indicated stall speed also increases because the same angle of attack correlates with higher speeds in thinner air. This understanding clarifies why this answer is correct.