What can severe fatigue cause a pilot to do during cruise flight?

Severe fatigue can significantly impair a pilot's performance, leading to major risks during flight operations. In the context of cruise flight, fatigue can diminish cognitive functions and reaction times, substantially increasing the likelihood of the pilot falling asleep. Although pilots may be trained to manage their fatigue and understand its impact, severe levels can overwhelm these strategies and cause lapses in awareness, making it difficult to maintain vigilance.

In contrast, the other options suggest enhanced abilities or improved performance. However, fatigue negatively affects a pilot’s cognitive processing, decision-making, and overall situational awareness. Therefore, rather than enhancing navigation skill or communication, severe fatigue typically leads to detrimental outcomes, making the risk of falling asleep during flight a critical concern for pilot safety.