At higher altitudes, the stall speed (IAS):

At higher altitudes, the stall speed in indicated airspeed (IAS) actually increases. This phenomenon can be attributed to the changes in air density as altitude increases. As an aircraft climbs, the air becomes less dense, which results in a reduction in lift generated by the wings at a given angle of attack.

Stall speed is influenced by the need for a certain amount of lift to counteract the weight of the aircraft, and since lift is directly related to air density, reduced density requires a higher true airspeed (TAS) to achieve the same lift. While the indicated airspeed can remain somewhat constant when considering the stall margin, the actual stall speed in terms of flying characteristics rises due to the increase in required speed to maintain sufficient lift.

Understanding this principle is crucial for pilots, as they must account for increased stall speeds at higher altitudes to ensure safe operations and avoid inadvertent stalls during critical phases of flight.