**Air Humidity** (copied and pasted from http://www.flyana.com/dehydration.html )
n-flight air is drier than any of the world's deserts. Relative humidity is 20-25% in the Sahara or Arabian deserts, while optimum comfort is around 50% humidity.
In-flight cabin humidities gradually fall on long-distance, high-altitude flights in many cases approaching 1%.
Basically, there's no way to avoid the fact that your body will become dehydrated to some degree as a result of flying long distances in near-zero humidity in commercial jet cabins. So we need to be mindful of our water intake en route, and also remember to drink plenty of pure water for s