Which factor does NOT commonly affect pilot performance?

In-flight comfort plays an important role in overall aviation safety and performance. While it can influence how a pilot feels during a flight, it is not typically considered a critical factor that directly affects pilot performance in the same way that fatigue, stress, and dehydration do.

Excessive fatigue can severely impair decision-making, reaction times, and overall cognitive function. High stress levels can lead to distractions and hinder a pilot's ability to concentrate on tasks. Chronic dehydration is known to affect physical performance and cognitive function, leading to decreased alertness and increased fatigue.

In contrast, in-flight comfort encompasses elements such as seat ergonomics, temperature, and noise level. Although these factors can enhance or detract from the overall flying experience, they do not have the same direct, measurable impact on performance levels. Hence, while comfort is relevant, it is not a factor that commonly affects a pilot’s performance as critically as the other choices.