Which altitude factor contributes to increased stall speed?

In understanding stall speed, it's important to consider the factors that influence it. Stall speed is the minimum speed at which an aircraft can maintain controlled flight. One major factor that affects stall speed is weight.

When the weight of an aircraft increases, the stall speed also increases. This is because a heavier aircraft requires more lift to maintain level flight, which in turn necessitates a higher angle of attack. As the angle of attack increases, the aircraft is closer to its critical angle of attack where stall occurs, therefore raising the stall speed.

Air density plays a crucial role as well; as altitude increases, air density decreases. This reduction means that the wings produce less lift for a given airspeed, necessitating a higher true airspeed for stall, which translates to an increased stall speed at higher altitudes. In contrast, if air density were increased, it would allow for lower stall speeds.

Ground effect also influences stall speed but mainly during landing and takeoff phases near the ground. It doesn't contribute to an increased stall speed generally at higher altitudes.

Therefore, the correct answer relates to the understanding that increased weight leads directly to an increase in stall speed.