Travel Dehydration is Real
Dehydration is a major issue when traveling by airplane. In an average 10-hour flight, men can lose approximately two liters of water and women around 1.6 liters.
The air circulation system of any aircraft must take in breathable air from the outside of the plane and deliver it to the passengers as it simultaneously cycles out the old air. However, the air outside of a plane at 35,000 feet tends to be extremely dry, with a humidity of only 10-20%. In comparison, the relative humidity of the Sahara Desert is about 25%!
When the air around you is dry, water from your nose, eyes, mouth and throat is attracted to the drier air molecules around you, in a process similar to evaporation. Therefore, while you might feel as though you are properly hydrated before traveling, over the course of a flight, your body will lose a great deal of its water to the dry air around you.
There is also a second factor that air travelers must deal with; when the air is dry, the cilia in your throat and nose don’t function as effectively to catch and eliminate airborne pathogens and irritants. So, it can actually be easier to get sick on a plane, even though the air is being recycled and circulated throughout the flight.
So, next time you see the flight attendant passing by, skip the soda and ask for water instead!