Should I avoid alcohol and coffee when flying?

You do not have to avoid them entirely, but both can contribute to dehydration and disturbed sleep. Alternating each drink with water and keeping intake modest helps you arrive feeling better.

Can I bring my own water through security?

You generally cannot bring liquids over 100ml through security, but you can take an empty reusable bottle and fill it after the checkpoint at a fountain or cafe. Many airports now have refill stations.

How to Stay Hydrated on a Flight

Q: How much water should I drink on a flight?

A common rule of thumb is to drink roughly a cup of water for every hour in the air, and more on very long flights. Listen to your body, sip steadily rather than gulping, and adjust for your size and activity. If you have a medical condition, follow your doctor's advice.

Q: Why does flying dehydrate you?

Cabin air at altitude is very dry, often below the humidity of a desert, which increases moisture loss through your skin and breathing. Alcohol and caffeine can add to fluid loss, so the effect builds over a long flight.

Reviewed by the ScanFlyGo team · Last updated: August 2026. This is general comfort advice, not medical guidance — follow your doctor for any health condition.

Quick answer

Cabin air is extremely dry, so drink water steadily throughout the flight — roughly a cup an hour is a good target — carry an empty bottle to fill after security, and go easy on alcohol and caffeine. Small habits like a moisturiser, lip balm and skipping salty snacks make a long-haul flight noticeably more comfortable and help you land feeling fresher.

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Why flying dries you out

At cruising altitude, cabin humidity is very low — frequently drier than a desert. Your body loses moisture through your breath and skin, and over a long flight that adds up. Combined with sitting still for hours and the occasional in-flight drink, mild dehydration is one of the main reasons people step off a plane feeling groggy, headachy or puffy.

How much to drink

There is no single perfect number, but a widely used guide is about one cup (around 240ml) of water per hour in the air, and a bit more on ultra-long routes. The goal is steady sipping rather than downing a bottle at once. Pale-yellow urine is a simple sign you are keeping up. If you have a heart, kidney or other condition, follow your doctor's advice on fluid intake instead.

Flight length	Rough water target
Short-haul (1–3 hrs)	1–3 cups
Medium (3–6 hrs)	3–6 cups
Long-haul (7+ hrs)	7+ cups, sipped steadily

Bring your own bottle

Security rules mean you cannot carry a full bottle of water through the checkpoint, but an empty reusable bottle is fine. Fill it at a fountain, refill station or cafe after security and you will not be relying on small in-flight cups. Ask cabin crew to top it up during the flight too — most are happy to.

What to go easy on

Alcohol: pleasant but can worsen dehydration and disturb sleep. Alternate with water and keep it modest.
Caffeine: coffee and strong tea are fine in moderation; balance them with extra water.
Salty snacks: crisps and pretzels can leave you thirsty and puffy — pair them with fluid.
Very sugary drinks: they hydrate less effectively than plain water.

Extra comfort habits

Hydration is not only about water. A little face moisturiser and lip balm counter the dry air, and saline nasal spray or eye drops help if your nose or contact lenses dry out. Get up and move every couple of hours to keep circulation going, which also helps you feel less sluggish. These small steps compound into a much better arrival.

Hydration and jet lag

Staying hydrated will not cure jet lag, but dehydration makes the symptoms feel worse. Arriving well-watered, having limited alcohol and having moved around gives your body an easier start when you adjust to a new time zone. Pair it with daylight and a sensible first-night sleep for the best results.

Frequently asked questions

How much water should I drink on a flight?

Roughly a cup per hour, more on very long flights, sipped steadily. Adjust for your size and follow medical advice if relevant.

Why does flying dehydrate you?

Cabin air at altitude is extremely dry, increasing moisture loss through skin and breathing; alcohol and caffeine can add to it.

Should I skip alcohol and coffee?

Not necessarily, but keep both modest and alternate with water to arrive feeling better.

Can I bring water through security?

Not over 100ml, but carry an empty bottle and fill it after the checkpoint at a fountain or refill station.

The bottom line

Staying hydrated on a flight is simple: sip water steadily, bring an empty bottle to fill airside, go easy on alcohol and salt, and add a few comfort habits like moisturiser and movement. Do that and you will land far fresher. Search your next flight on ScanFlyGo, compare popular routes, and track it live on the day you travel.

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