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Why do airlines always give you bottled water? The real reason

General

Image: Lukas Souza

Image: Lukas Souza

Flying facts

Why do airlines always give you bottled water? The real reason

Some people board a plane and fall asleep before takeoff, while others feel every turbulence and get nauseous. Which one are you? At 35,000 feet, your body goes through a series of changes, and different bodies react differently. Why do your ears pop? Why do some people feel airsick? Today, we’re breaking down what really happens to your body when you fly and the surprising reasons behind those sensations.

Most people feel their ears "clog" or pop during a flight, and there’s a reason why. This is known as ear barotrauma, or "airplane ear," and it happens when air pressure changes quickly during takeoff and landing. As the plane quickly climbs or descends, the pressure outside your body shifts faster than the pressure in your middle ear can equalize. That imbalance is what causes the discomfort or popping sensation.

How to avoid it? Chewing gum, swallowing, or yawning can help open the Eustachian tubes (a small passage connecting the middle ear to the back of the nose and throat) and relieve the pressure.

Swollen feet and ankles (edema) are one of the most common temporary issues during air travel. But why does it happen? On most flights, especially in economy class, you’re sitting for long periods with your feet down and little room to move. That position slows blood flow, allowing fluid to pool in your lower legs and feet. To reduce the swelling, try to move your legs regularly during flight, flex and rotate your ankles in your seat, and, when it’s safe to do so, stand up or walk the aisle. For longer flights or if you’re prone to swelling, compression socks can also help.

Your circadian rhythm is your body’s 24-hour internal clock, the system that regulates sleep, hormone release, and body temperature. But when you fly across time zones, that clock gets "out of sync". This mismatch between your internal time and the local time at your destination is what causes jet lag. Your body might be ready to sleep when it’s daytime, or feel hungry in the middle of the night, leading to fatigue, insomnia, and even digestive issues.

Bottles of water and other drinks are very common on flights, even short ones. But it’s not just a nice touch; there’s a real reason for it. At that altitude, cabin air is extremely dry, often with humidity below 20%, which can quickly dehydrate your body. That’s why you start to feel thirsty. It’s a good idea to drink plenty of water on the day you fly, but don’t overdo it. Around 2 to 3 liters a day is generally enough, and let’s be honest, no one wants to be stuck making constant trips to the bathroom at 35,000 feet.

Many people notice changes in their skin during a flight: some feel unusually dry, others get itchy, and some even break out. So what’s going on? The dry cabin air is the main culprit. With humidity often below 20%, your skin loses moisture, just like your eyes and airways. That dryness can weaken your skin’s barrier, sometimes leading to irritation, or, for some people, excess oil production that can trigger acne. To help prevent this, use a good moisturizer before and during the flight; it helps your skin stay balanced, even in that dry environment.

"Jet belly" is the playful name experts give to the bloating many people feel during a flight. To explain this, they use Boyle’s Law: as air pressure drops, gas expands. Inside a plane cabin, the gas in your digestive system can expand by 20 to 30%. That’s what causes the tight, bloated, and uncomfortable feeling. To minimize it, try to avoid carbonated drinks and heavy, salty, or fatty foods before and during the flight. Staying hydrated also helps, and if it’s allowed, getting up for a short walk can keep things moving inside, too, easing the discomfort.

Have you ever gotten off a plane with surprisingly bad breath, even if you barely slept? You’re not imagining it: there’s a real reason. Inside the cabin, the air is extremely dry, and that low humidity can dehydrate your body, reducing saliva production. Since saliva helps control bacteria, less of it means odor-causing bacteria can appear more easily. If you want to land feeling fresh, keep a toothbrush or mints in your carry-on for a quick fix before you get off the plane.

Ever feel like food tastes different on a plane? Well, it turns out your sense of taste and smell actually change because of lower air pressure and low humidity in the cabin. These conditions dry out your nasal passages and mouth, and since smell plays a big role in flavor, that dryness dulls your ability to taste, especially sweet and salty notes. According to some studies, your sensitivity can drop by around 20–30%, but airlines know this, which is why many in-flight meals are more heavily seasoned than you’d expect on the ground.

Conditions inside the aircraft cabin also affect oxygen levels. While cabins are pressurized and carefully monitored, the air at that altitude still contains less oxygen than at sea level. Combined with long periods of sitting still, this can make your body work a bit harder to deliver oxygen to your cells, leaving you feeling slightly tired or sluggish. To help counter this, stay well hydrated and try to get a good night’s sleep before your flight.

If you thought flying only affects your body, think again: your mood can shift, too. The lower oxygen levels in the cabin can slightly affect cognitive function, making it a bit harder to manage your emotions. That might explain why a movie hits harder at 35,000 feet or why your seatmate is suddenly tearing up. Add in the stress of travel, disrupted routines, and long hours in a small space, and it’s no surprise your emotions can feel a bit intense during a flight.