Flight deck is the most dry section in an aircraft with almost no (read: close to zero) moisture content in the air. It is in fact World’s most dehydrating working environment.
All of our organs, including our brains, need water to function properly. If you’re dehydrated, your body isn’t running well — and that can lead to stress.
Already a modest dehydration, increase the Cortisol level. Cortisol is one of our stress hormones. The extremely dry air in flight deck makes it harder to remain in a good hydrated status. A striking humidity increase can help to keep stress levels down.