Why do we get dehydrated while flying?



Does it have something to do with the altitude affecting certain organs, or is it entirely unrelated?

In: Biology

The air is very dry.

Also, because of the lower partial pressure of oxygen in the pressurized cabin, you breathe deeper and faster to compensate, thus losing more water


The air within the plane is dry and warm. It is intentionally kept that way to minimize the effects of corrosion on the metal parts within the plane.

Some of the newer planes are using more carbon fiber in their construction which means that the ambient humidity in the plane can be raised without risking damage to the plane itself.

Dehydration is a contributing factor of jet lag. Also, consumption of alcohol while flying adds to the dehydration. To combat the effects of dehydration, the staff aboard the plane encourage frequent consumption of non-dehydrating liquids.

The air is dry. 40% of the air is recycled and 60% is pumped in from outside. However at altitude, the “thinness” of the air means it can hold less water vapor per volume as compared to air closer to sea level. So as the air is scooped up and slightly compressed to keep the cabin at pressure, it slowly dilutes the more moist air from the ground with dryer air. Meaning your body is forced to use more water to produce the saliva it needs to keep your mouth and throat moist.

It doesn’t help that the airlines never really provide passengers with an appropriate amount of water because 1)water is heavy and carrying that much water would severely reduce fuel efficiency/capacity 2)having that many people need to use the bathroom regularly on a plane would become problematic fast.

It’s dry air sucked in from the outside, which is very cold, and very dry (-40 <1% humidity), and when you heat cold dry air, you get warm even dryer air. Depending on the age of the aircraft it is either engine bleed air, or outside air pulled in and compressed, or a mix of the two. Both are very dry. The humidity from people breathing helps moisten the air up and it’s more comfortable if the air is recirculated in the cabin as it keeps the air a little more humid.

It’s also much lower pressure (Usually equivalent of 6000 to 7000 feet) at cruising altitude inside of the aircraft. Lower pressure reduces the boiling point of water and increases the rate it evaporates. The lower the air pressure, the lower the vapor pressure and the more easily water boils and evaporates. This is why food often has high altitude instructions that require you to cook it longer because the food doesn’t get as hot because the boiling point is lower. Water can never get hotter than the boiling point so lower boiling point, lower temp, longer cook.

Really though most of what happens is not dehydration, it’s just drying of the mouth, sinuses, and throat, which prompts the body to feel thirsty.

You do? (I’ve only been on a plane 6x my whole life.)