Question 1

How much water should I drink on a plane?

Accepted Answer

About 8 fl oz (one cup) per hour of flight. Cabin air humidity is only 10–20% — much drier than a typical office or home — so you lose water faster through breathing and skin evaporation.

Question 2

Why do you get dehydrated on a plane?

Accepted Answer

Aircraft cabins are pressurized at low humidity (10–20%). At these humidity levels your body loses moisture through your skin and breath faster than normal, even if you don't feel thirsty.

Question 3

Should I avoid alcohol on a flight?

Accepted Answer

Yes, especially at the start of a long flight. Alcohol is a diuretic, and its effects are amplified at altitude due to lower oxygen saturation. Stick to water or juice for most of the flight.

Question 4

Does coffee dehydrate you on a flight?

Accepted Answer

At normal amounts, coffee barely dehydrates you on the ground — research shows it hydrates similarly to water. On a flight you're already losing more water than usual, so it's smart to have water alongside your coffee rather than instead of it.

Flight Hydration Calculator

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