What symptom indicates dehydration while flying?

Fatigue is a key symptom that indicates dehydration, especially while flying. Dehydration can lead to a decrease in overall blood volume, which in turn affects the oxygen delivery to the muscles and brain. When pilots experience dehydration, they often feel tired or fatigued because their bodies are not functioning at optimal levels. This fatigue can significantly impair cognitive functions, reaction times, and overall performance, making it crucial for pilots to maintain proper hydration during flights. Recognizing fatigue as a sign of dehydration is important for ensuring safety in aviation operations.

In contrast, increased energy, improved mental alertness, and enhanced hydration are all unlikely outcomes of dehydration. These options do not align with the physiological responses experienced during a dehydrated state.