Why You Lose 1.5 Liters of Water on a 3-Hour Flight – And Proven Ways to Stay Hydrated in the Air
Air travel rapidly increases day by day, making it easier for passengers to reach their destinations faster and safer. But many passengers experience dehydration. The fact is, a human body may lose up to 8% of water during a typical flight, like 1.5 liters for a 3-hour flight.
Due to loss of fluid in the body, it might affect your body’s health, energy levels, and overall comfort in the air.
In this article, we discuss why this dehydration occurs during flight, what it does to your body, and how you can prevent its effect by adopting smart in-flight habits.
Table of Contents
Why Do You Get Dehydrated on Flights?
Low Cabin Humidity
The fact is, aircraft cabins are typically pressurized to mimic an altitude between 6,000 and 8,000 feet, even with planes flying at higher altitudes.
This pressurization ensures safe and comfortable breathing. The air is much drier at that altitude, the humidity is less than 20% – which is much less (30 to 40 percent) on the ground. This allows normal breathing and reduces the risks that occur due to high altitude.
In such dry conditions, moisture is lost from our body through the skin, breath and eyes. And other passengers will feel more fluid loss due to respiration when our lungs work hard to inhale the air.
Recycled Air
The aircraft environmental control system removes moisture from our breath and keeps the air constantly recirculated. Although this process repeatedly improves cabin air, it also increases fluid loss.
Lack of Movement
When the passenger is sitting for a long period without standing, stretching or walking, our body’s circulation slows down. Which contributes to water retention in the lower limbs and makes them feel an overall sense of fatigue. Due to there being less water in the body, we do not feel thirsty, until there is no dehydration.
Caffeine and Alcohol Consumption
Many passengers enjoy a cup of coffee and a glass of wine during the flight. Both are diuretic drinks which increase urine production and also cause fluid loss. There is humidity in the cabin from the beginning and after drinking too much, dehydration occurs even more quickly.
How Much Water Do You Actually Lose?
According to aerospace medical experts, an average adult loses around 1.5 liters of water in a 3-hour flight. This number increases if we talk about international flights, in which 2–3 liters of fluid are lost in an 8 to 10-hour flight, which is equivalent to the body’s fluid requirement for an entire day.
You may notice common dehydration symptoms like:
- Dry mouth or lips
- Headaches
- Dizziness or fatigue
- Muscle cramps
- Dry or itchy eyes
- Jet lag intensifying
How to Stay Hydrated During a Flight
Start Hydrating Before You Board
Keep drinking water during the entire flight and keep yourself hydrated. Drink water at least one day before the flight, at most 8 to 10 glasses of water so that our body gets well hydrated to adapt to the dry environment of the aircraft.
Tip: Avoid salty snacks or heavy meals that can cause fluid retention or bloating.
Carry a Reusable Water Bottle
The water you get inside the aircraft is usually in very small cups, so keep a refillable water bottle with you and ask the cabin crew to fill it. Many airports offer filter water refilling stations.
Tip: Opt for a bottle with a built-in filter if you’re traveling internationally.
Drink Water at Regular Intervals
Try to consume at least 250 ml of water every hour during your flight journey, i.e. consume at least 750 ml of water on a 3-hour flight. This will make up for the shortage of water.
Avoid waiting until you feel thirsty—by then, you’re already dehydrated.
Limit Caffeine and Alcohol
Avoid coffee, tea and alcoholic drinks during your flight journey. If you consume them, then the chances of getting dehydrated increase. It is better to consume some healthy and water-based food.
Eat Hydrating Foods
Select good fruits to eat, such as watermelon, oranges, cucumber, and apples, which have a high water content. Ignore snacks that draw water from the body and increase the risk of dehydration.
Use a Hydrating Face or Eye Mist
Some passengers carry a portable humidifier with them which increases the humidity around the seat. And another way is to carry small hydrating facial mist or eye drops which help you stay fresh and prevent discomfort, as dry skin and eyes are very common issues on flights.
Key Takeaways
- Aircraft cabins have extremely low humidity (<20%), leading to rapid fluid loss.
- You can lose up to 1.5 liters of water on a 3-hour flight.
- Start hydrating the day before traveling and continue throughout your journey.
- Avoid caffeine, alcohol, and salty foods inflight.
- Use smart tools like refillable bottles, hydrating snacks, and facial mists.
At the End
Aircraft manufacturers’ new planes like the Boeing787 and Airbus A350 can maintain cabin pressurization at lower cable altitude of around 6000 feet, which will provide more comfort and reduction in fatigue for passengers.
Now the next time you travel by flight, do not forget to drink an extra glass of water, which will make you feel good even during the entire journey.
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