Sky-High (de)Hydration

Your essential guide to combatting dryness and staying refreshed on flights.

Imagine you're cruising above the clouds, sipping on your favorite drink, and suddenly you feel your skin getting parched. No, it's not just you – the air up there is as dry as Death Valley. Airplane cabins are known to be dehydrating environments. But why is that?

Low Humidity Levels

Why are Planes Designed to be Dry?

Why Should You Care?

Low humidity levels

Most commercial airplanes are pressurized to resemble conditions at about 6,000-8,000 feet above sea level. So although you're flying at 35,000 ft, your body thinks it's at 8,000 ft. This is great for breathing but it also means the air is much drier. The air at high altitudes has very low humidity, and the air brought into the cabin from the outside retains this low humidity. To ensure that the cabin air remains fresh, part of the air in the cabin air is recirculated. While modern airplanes have sophisticated filters to clean this air, the process does not add moisture, contributing to the overall dryness.

The humidity level in airline cabins typically ranges from 4-7% relative humidity, which is far too dry – drier than any of the driest climates on Earth. For comparison, the average home has a humidity level of about 30-50%. The Sahara Desert has an average relative humidity of 25%.

There are some aircraft that come equipped with humidifiers, such as the Boeing 787 and Airbus A350. These are, however, typically only found in the flight deck or crew rest bunks. The 787 maintains 10-15% relative humidity with its lower cabin altitude and optional humidifiers, making it one of the best cabin environments in the air.

The world's most dehydrating office

A flight deck is essentially the driest and most dehydrating office ever.

All of our organs, including our brains, need water to function properly. The extremely dry air in the flight deck makes it harder to remain in a well-hydrated state. If you’re dehydrated, your body increases its cortisol levels- which in turn leads to increased stress.

Why are planes designed to be dry?

There are some airplane models- like the 787, 777X, and A350- that come with optional humidifiers for the flight deck and crew rest areas. These can also be available for first/business class in some cases. By and large, if you ran a humidifier you would end up lowering the life of the airplane and increasing costs.

A higher humidity environment is conducive to mold and bacteria growth- which would require more deep cleaning/dehumidification. It's corrosive and leads to more wear/tear on the plane. Also, to humidify the air, you need to add water. Water is heavy (around 8 lbs/gallon) and expensive to transport.

Another fun fact: people and things smell worse in humidity. Humid air transmits odor more readily, so smelly people and things in a dry airplane smell subjectively and objectively less bad than the same smelly people and things in a humid airplane.

Since low cost is the number one deciding factor for the average passenger, I'm sure most would opt for a low-humidity plane and a little bit of discomfort so they can save a buck.

Why should you care?

Understanding the dryness in airplane cabins isn't just about comfort; it's about health too. In a low-humidity environment, moisture evaporates from the body more quickly. This includes moisture from the skin and the respiratory tract, leading to feelings of dryness and dehydration. The air in the cabin can cause mucous membranes in the nose and throat to dry out, which can lead to discomfort and possibly increase susceptibility to infections.

To mitigate the dehydrating effects of flying, it's advisable to drink plenty of water before and during the flight and to avoid diuretics like caffeine and alcohol. Keeping hydrated and moisturized can help ward off those pesky travel-related nuisances like jet lag, fatigue, and a heightened susceptibility to colds.

So, the next time you fly, remember that while you're soaring through the skies, a little bottle of water, some saline solution, and a good moisturizer can make your journey much more enjoyable.

Fly Smart, Fly Hydrated

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