10 ways to stay healthy on a long flight, from hydration to jet lag

A long-haul flight asks the body to do something it rarely does on the ground. It has to sit almost still for many hours in dry air, at close quarters with many other people, while drifting away from its usual sleep schedule. Each part of that setup creates its own small strain. Together, they explain why travelers often step off a plane feeling stiff, parched and out of sync with the local clock.

The cabin itself is the first factor. Air on commercial jets carries very little moisture. Skin, eyes, nose and throat can dry out over the course of a trip. Stillness is the second. Sitting for long stretches slows blood flow in the legs. For some travelers, that raises the risk of deep vein thrombosis, a clot that forms in a deep vein.

Sleep and timing add another layer. An upright seat, cabin noise and light make rest hard to come by. Crossing several time zones leaves the body clock out of step with local time at the destination, which is the root of jet lag. A shared cabin also means shared surfaces, from tray tables to armrests, handled by many passengers.

None of these pressures requires elaborate preparation. Knowing how to stay healthy on a long flight comes down to small, repeatable habits that each address one problem. Steady water intake offsets dry cabin air, and lighter meals sit more comfortably during hours in a seat. Movement, seated exercises and, for some travelers, compression socks support circulation. Planning sleep around the destination's time zone eases the shift. Basic hygiene limits contact with germs. Moisturizer, saline spray and eye drops ease dry skin, eyes and nasal passages.

The 10 habits below are a practical selection rather than a complete program. Each one stands on its own. Readers can pick the ones that fit a particular trip, seat or schedule. Most cost little and need nothing beyond what fits in a carry-on bag. Rules on liquids, food and medicines vary by airport, airline and country. Checking them before departure avoids surprises at security or customs.

Travelers $TRV with medical conditions should get personal advice first. Anyone with a history of blood clots, recent surgery, pregnancy or another health concern should talk to a doctor before a long flight. That conversation can cover whether compression stockings make sense and how to time regular medications across time zones.

Illustration: Quartz

Sip water at regular intervals from boarding to landing to stay comfortable on a long-haul flight. Cabin air on commercial jets is very dry, and steady intake keeps the body ahead of that dryness instead of playing catch-up.

The dryness has a physical cause. Much of the air supplied to the cabin is drawn in from outside the aircraft at cruising altitude. Air at that height is extremely cold and holds very little moisture. As a result, cabin humidity stays low for the whole journey.

Low humidity increases the moisture the body loses through ordinary breathing. Over many hours, that loss can show up as a dry mouth, a headache or fatigue. Those are common signs of mild dehydration. They are easy to mistake for ordinary travel tiredness.

Small, frequent drinks suit a flight better than one large one. Drinking a big volume at once can mean several lavatory trips in quick succession. Regular sips spread intake evenly across the journey. One workable rhythm is a few mouthfuls whenever a meal or drink service passes, with more in the long gaps between services.

Thirst alone is not always a reliable guide, particularly when a traveler is distracted or asleep for long stretches. Urine color offers a simple check. Pale yellow generally indicates good hydration, while darker urine suggests a need to drink more.

Access to water is the main practical hurdle. A common approach is to carry an empty reusable bottle through the security checkpoint. Travelers $TRV then fill it at a fountain or bottle-filling station on the other side. Not every airport has filling stations, and container rules differ from one airport to the next. A quick look at the departure airport's guidance settles both questions.

On board, cabin crew can usually refill a bottle or bring extra cups between meal services. On long-haul routes, water is often available from the galley throughout the flight. Asking a crew member directly can be quicker than waiting for the next drink cart.

Where the bottle sits matters too. One stowed in the overhead bin tends to go untouched for hours. Keeping it in the seat-back pocket puts it within reach whenever thirst or habit prompts a sip.

Illustration: Quartz

Getting up to walk the aisle whenever the seatbelt sign is off keeps blood moving through the legs during a long-haul flight. Hours of sitting slow circulation in the lower legs, and a short walk restarts it.

The calf muscles do much of the work of returning blood from the feet to the heart. Each time they contract, they squeeze the veins and push blood upward. When a passenger sits still for hours, those muscles barely move. A bent knee and hip in a cramped seat can also press on the veins behind them.

For some travelers, that slowdown raises the risk of deep vein thrombosis, or DVT. This is a blood clot in a deep vein, usually in the lower leg or thigh. The main danger is that part of a clot can break loose and travel to the lungs. That condition, a pulmonary embolism, is a medical emergency.

Warning signs of DVT include swelling, pain, tenderness or warmth in one leg. These symptoms do not always appear during the flight. They can show up in the days after landing. Anyone who notices them should seek medical care. Sudden shortness of breath or chest pain calls for emergency help.

A common rhythm is to stand up and walk every hour or two while awake. A trip to the lavatory counts, and so does a slow lap to the back of the cabin and back. Booking an aisle seat makes this easier. It removes the need to wake or climb over neighbors each time.

Timing matters on a busy aircraft. Meal and drink carts can block the aisle for long stretches. The quieter periods after service tend to leave the aisle clear. The area near the rear galley sometimes has room for a brief standing stretch, such as rolling the shoulders or reaching the arms overhead. Keep it short and step aside for crew and for passengers waiting for the lavatory.

Crew instructions take priority over any walk. Return to your seat when the seatbelt sign comes on or when crew ask passengers to sit. Turbulence can arrive without warning. Keeping the belt loosely fastened whenever seated protects against sudden jolts between walks.

Illustration: Quartz

Ankle circles, foot points and flexes, and alternating heel and toe lifts keep the calf muscles working without leaving the seat. These small moves help push blood out of the lower legs during long stretches when standing up isn't possible.

The calf muscles act as a pump for the veins in the lower leg. Each time they contract, they squeeze those veins and help move blood back toward the heart. When a passenger sits motionless for hours, that pump does very little work. Blood can then pool in the legs. For some travelers, that pooling raises the risk of deep vein thrombosis, a blood clot that forms in a deep vein.

Ankle circles need only a few inches of space. Lift one foot slightly off the floor and rotate it slowly in a circle, then reverse direction. Switch to the other foot and repeat.

Pointing and flexing works the same muscles from a different angle. Point the toes away from the body as far as is comfortable, then pull them back toward the shins. The calf should tighten and release with each cycle.

Heel and toe lifts can be done with both feet flat on the floor. Raise the heels while keeping the toes down, then lower them and lift the toes instead. Alternating between the two keeps the lower legs moving even in a cramped row.

These exercises suit moments when the seatbelt sign is on, a meal cart blocks the aisle or a seatmate is asleep. Some airlines show seated exercise routines on seatback screens or in in-flight magazines.

Posture matters too. Sitting with the legs crossed for long periods can press on the veins behind the knee. Bags stowed in the footwell also limit how far the feet and ankles can move. Moving a carry-on into the overhead bin frees up room for the exercises.

Seated movement does not replace medical advice. Anyone with a past blood clot, recent surgery, pregnancy or other clot risk factors should check with a doctor before a long flight. A doctor can say whether extra precautions make sense. Swelling, pain, warmth or redness in one leg after a flight can signal a clot and needs prompt medical attention. Sudden shortness of breath or chest pain can mean a clot has reached the lungs. That is a medical emergency.

Illustration: Quartz

Graduated compression stockings apply steady, gentle pressure to the lower legs that helps blood flow back toward the heart. They are commonly recommended for travelers at higher risk of blood clots on long flights. They are not a fit for every passenger.

The word "graduated" describes how the pressure is distributed. The fabric squeezes most tightly at the ankle and loosens gradually up the calf. That gradient supports the leg veins as they move blood upward against gravity. Hours in a cramped seat work against that process. This is why the legs get so much attention in long-haul health advice.

Many travelers also wear compression socks to limit the ankle and foot swelling that tends to build during a long stretch of sitting. Swollen feet can make shoes feel tight by the time the plane lands.

Fit matters more than style or color. Stockings are sized by measurements of the ankle and calf, and sometimes by leg length. A pair that is too loose does little. A pair that rolls down or bunches at the top can form a tight band behind the knee. That band restricts circulation rather than helping it.

Knee-high styles are a common choice for air travel. They are easiest to put on before leaving for the airport, when the legs are least swollen.

Pharmacies and travel stores sell lighter-pressure versions. Stronger grades are usually measured, fitted or prescribed by a clinician. The pressure is labeled in millimeters of mercury, the same unit used for blood pressure readings.

Compression socks are not suitable for everyone. Added pressure on the legs can cause harm for people with some circulation or skin conditions, including peripheral artery disease. Anyone with numbness in the feet should also get medical advice before wearing them.

Travelers $TRV with a history of blood clots, recent surgery or a current pregnancy should talk to a doctor before a long flight. The same applies to anyone with other clot risk factors. A doctor can say whether stockings make sense, which pressure grade to use and whether other precautions are needed. Stockings work alongside regular movement during the flight, not in place of it.

Illustration: Quartz

Cutting back on alcohol and caffeine during a long flight protects sleep and avoids adding to the dryness of cabin air. Both drinks can disrupt the rest a traveler needs to arrive alert.

Alcohol is a diuretic. It increases urine output, and the body loses more fluid than it otherwise would. In an aircraft cabin where humidity is already low, that loss can deepen the sense of dehydration. A headache, fatigue and a dry mouth can follow a traveler off the plane and into the first day at the destination.

A drink can make it easier to doze off in an upright seat. The trade-off comes later. Alcohol tends to fragment sleep in the second half of the night. It also cuts into the deeper, more restorative stages of sleep. Rest that starts quickly after a glass or two of wine is often lighter and more broken.

Alcohol carries a specific risk for anyone taking sleep medication on board. Mixing it with sedatives or sleeping pills can intensify drowsiness and slow breathing. Travelers $TRV who plan to use any sleep aid should ask a doctor or pharmacist about interactions with alcohol before the trip.

Caffeine creates the opposite problem. As a stimulant, it blocks adenosine, a chemical that builds up in the brain during waking hours and drives the urge to sleep. Its effects can linger for several hours after the last cup.

Timing shapes how caffeine affects a flight. A coffee at the gate before an overnight flight can make sleep on board harder to reach. On a daytime flight that lands in daylight, a morning cup may fit the schedule. Limiting caffeine to the hours a traveler intends to stay awake keeps it from competing with planned sleep.

Caffeine also turns up in less obvious places. Black and green tea, cola, energy drinks and chocolate all contain it. Decaffeinated coffee still has a small amount.

The drinks cart usually has alternatives. Water, sparkling water, juice and caffeine-free herbal teas such as chamomile or peppermint offer something warm or flavored without a stimulant. A single glass of wine with dinner places less strain on hydration and sleep than steady refills across a long flight.

Illustration: Quartz

Jet lag happens when the body clock stays set to home while the local clock moves ahead or behind. Shifting sleep and light exposure toward the destination's schedule, starting before departure, helps the body catch up sooner.

The body clock, known as the circadian rhythm, is governed by a small region of the brain called the suprachiasmatic nucleus. Light is the signal it responds to most strongly. A traveler who crosses several time zones can end up wide awake at 3 a.m. and drowsy at lunch. Other common effects include poor concentration, irritability and an unsettled stomach.

Direction matters. Flying east usually feels harder than flying west. Heading east shortens the day. The body clock tends to resist moving earlier more than it resists moving later.

Preparation can begin a few days before the trip. For an eastbound flight, go to bed and wake up a little earlier each night. For a westbound flight, push both a little later. Small steps are easier for the body to absorb than one abrupt change.

On boarding, set a watch and phone to destination time. That switch makes it easier to plan the rest of the flight around the new schedule. If it is night where the plane is headed, try to sleep. If it is daytime there, stay awake, even if the cabin lights are dimmed.

Light is the strongest tool after landing. Time outdoors in daylight helps reset the body clock. After an eastbound trip, morning light tends to help most. After a westbound trip, light in the late afternoon and evening is usually more useful. Keep any nap on arrival day short. Hold off on a full night's sleep until local bedtime.

Melatonin is a hormone the body produces in darkness. Supplements containing it are sold to ease jet lag. They are available over the counter in the U.S. but generally require a prescription in the U.K. The right dose and timing depend on the person and the trip. Those decisions belong with a doctor or pharmacist. Melatonin can also interact with some medications.

For a stay of only a day or two, some travelers keep to home time rather than adjusting at all.

Illustration: Quartz

An eye mask, earplugs and a neck pillow tackle three things that keep many travelers awake in a plane seat: light, noise and a head with nowhere to rest. Together they make an upright seat a more workable place to sleep.

Light is a strong signal to the brain that it is time to be awake. Cabin crews dim the lights on many overnight flights. Reading lights, seatback screens and window shades opened by other passengers still leak through. A contoured eye mask that sits away from the eyelids blocks that light without pressing on the eyes. It also gives a sleeper their own darkness, whatever the people nearby are doing.

Noise on a plane comes in two forms. The engines and air system produce a steady, low drone for the whole journey. Conversations, announcements and service carts add sudden, sharper sounds on top. Foam or silicone earplugs are small, inexpensive and muffle both. Noise-canceling headphones work differently. They use microphones and electronics to counter constant low-frequency sound. That makes them well suited to engine hum. Some travelers wear earplugs under headphones for extra quiet.

A neck pillow keeps the head from dropping forward or rolling sideways once the body relaxes. That movement is what jolts many people awake and leaves the neck stiff after landing. U-shaped pillows are the familiar design. Turning one around so the thicker part sits under the chin gives more support to a head that tips forward. A window seat adds a wall to lean against.

Temperature can shift during a long flight, and the cabin often feels cool overnight. Layers such as a light sweater and warm socks are easier to adjust than a single heavy jacket. Anyone sleeping under a blanket should fasten the seatbelt on top of it, where crew can see it is buckled. That way crew have no reason to wake a sleeping passenger when the seatbelt sign comes on.

Reclining the seat helps, but the passenger behind shares that space. A quick glance back and a slow recline avoid knocking into a laptop or a drink. Crew typically ask for seats to be upright during takeoff and landing, and often during meal service as well.

Illustration: Quartz

Clean hands and wiped-down surfaces reduce the germs a traveler picks up in a crowded cabin. Wash with soap and water or use alcohol-based hand sanitizer, wipe the high-touch spots around the seat, and keep your hands away from your face.

A long-haul flight puts many people in a shared, enclosed space for many hours. Passengers touch the same latches, buttons and handles throughout the trip. The same seat may also serve several travelers in a single day as an aircraft flies one route after another.

Most of the surfaces a passenger handles sit within arm's reach of the seat. The tray table is the obvious one, because food and drinks rest directly on it. Armrests, the seatbelt buckle, the seatback screen and the window shade get touched often too. So do the overhead reading light and air vent controls.

A disinfecting wipe can go over each of these after sitting down. The job takes a minute or two. Letting the surface air-dry afterward gives the product time to work before anything touches it.

The minutes before eating are an important time to clean hands. Meals and snacks travel from fingers to mouth. Cleaning hands just before the tray arrives keeps germs off the food. The lavatory is the place to wash with soap and water on board.

A thorough wash covers the backs of the hands, the spaces between the fingers and the skin under the nails. Rinse well and dry completely. A paper towel can then be used to open the lavatory door on the way out.

Alcohol-based sanitizer is the practical option at the seat. It works less well on hands that are visibly dirty or greasy. In that case, soap and water are the better choice. A small bottle of sanitizer also has to meet the liquid rules at airport security, which vary by country.

Touching the face gives germs on the hands a route into the body. They can enter through the eyes, nose and mouth. Rubbing tired eyes, adjusting glasses and resting a chin on a hand are common moments on a long flight.

Some passengers also wear a face mask in the cabin, particularly during cold and flu season. Travelers $TRV with weakened immune systems or chronic health conditions can ask a doctor about extra precautions before a long trip.

Illustration: Quartz

Packing simple snacks such as nuts, fruit or crackers, and choosing lighter, less salty meals, lets travelers eat when they are hungry. It also helps them stay comfortable while seated for hours.

Cabin meal service runs on the airline's timetable, not the passenger's. On a long-haul flight, trays may arrive while a traveler is trying to sleep or long after hunger sets in. A small supply of food in a carry-on bag closes those gaps.

Foods that travel well are dry, sturdy and easy to eat in a narrow seat. Unsalted nuts, whole fruit such as apples or bananas, dried fruit, plain crackers and granola bars all fit that description. A homemade sandwich works for the early part of a trip if it is eaten within a few hours.

Security screening is the first rule to check. Many airports limit carry-on liquids to small containers, and soft foods can fall into that category. At U.S. checkpoints, the Transportation Security Administration treats items such as yogurt, hummus and peanut butter as liquids or gels. Solid foods generally pass through without that restriction, though screeners can ask to inspect them.

Arrival rules are the second check, and they vary by country. Many governments restrict fresh fruit, vegetables, meat and dairy brought in from abroad. The aim is to keep out pests and plant diseases. Australia and New Zealand enforce strict biosecurity checks, and travelers must declare food on arrival. The U.S. also requires passengers to declare agricultural products. Eating leftover produce before landing, or throwing it away on board, avoids the risk of a fine or a confiscated item.

The meals served on board call for the same planning. Heavy, rich dishes can leave a seated passenger feeling sluggish and bloated. Salty food can make the thirst that already comes with dry cabin air harder to manage. Picking the lighter option on the menu, or eating only part of a large tray, tends to sit more comfortably over hours in a seat.

Many long-haul carriers let passengers request a special meal, such as vegetarian or low-sodium, when booking or managing a reservation. These requests usually need to be made in advance. Each airline sets its own deadline, so it is worth checking before the day of travel.

A shared cabin also shapes what to pack. Some airlines ask passengers to avoid eating nuts when a traveler with a severe nut allergy is on board. Foods with strong smells linger in a closed cabin and reach nearby seats quickly.