What happens to stall speed (IAS) as altitude increases?

As altitude increases, stall speed in terms of indicated airspeed (IAS) actually remains relatively constant, but the true airspeed (TAS) associated with that stall speed increases due to the effects of decreased air density. Stall speed is primarily a function of the aircraft's weight and the characteristics of its wing, which are largely influenced by the air density.

Although the correct choice reflects the relationship between stall speed and density, it does not adequately address how stall speed is perceived in terms of indicated airspeed. In fact, stall speed in terms of IAS remains constant when considering the aircraft's weight and configuration. However, since air density decreases with altitude, the aircraft must fly at a higher true airspeed to maintain the same lift, which can create confusion about the stall speed in different phases of flight.

Therefore, one could clarify that as altitude increases, the indicated airspeed (IAS) at which stall occurs does not change significantly, while the true airspeed (TAS) does need to increase because the aircraft's wings are less effective in denser air. This outcome points towards the intricacies of how IAS and TAS differ at varying altitudes, leading to a deeper understanding of performance metrics in aviation.