Quick Answer
Jet lag comes from crossing time zones, not simply from flying long distances, so a flight to South Africa causes almost none while a flight to Australia or Japan causes plenty. The most effective prevention is shifting your sleep schedule a few days before departure, staying hydrated and avoiding alcohol on the flight, and getting bright light exposure at the right time once you land. Flying east is generally harder to adjust to than flying west.
Why Some UK Flights Cause Jet Lag and Others Don’t
Jet lag is caused by your body’s internal clock being out of sync with the local time at your destination, which means the number of time zones crossed matters far more than how many hours you spend in the air. This catches a lot of UK travellers out, since a long flight doesn’t automatically mean bad jet lag.
Flights from the UK to South Africa are a good example. Despite being a genuinely long flight, Cape Town and Johannesburg sit in a similar time zone to the UK, so there’s little to no jet lag at all. Compare that to a much shorter flight to Dubai or Delhi, which crosses several time zones and can leave you genuinely disoriented for days. Long-haul flights to the US East Coast, Australia or Japan cross the most time zones from the UK and tend to cause the worst symptoms.
Flying East Is Harder Than Flying West
Without any adjustment, your body naturally shifts by roughly one hour of time change per day, which means it can take over a week to fully adjust after crossing an ocean. Flying east compresses your day, forcing your body to fall asleep earlier than it wants to, which is consistently harder to adjust to than flying west, where your day simply gets longer.
This matters practically for UK travellers: a flight to Japan or Australia, both firmly east, tends to hit harder than a similarly long flight to the US West Coast, which is west and generally easier to recover from.
Before You Fly
Start shifting your sleep schedule two to three days before departure, moving bedtime and mealtimes incrementally closer to your destination’s schedule rather than attempting a sudden switch on travel day. Even a partial shift genuinely helps reduce the adjustment needed once you land.
Booking an evening flight where possible gives your body a natural advantage, since you’ll already be tired from a full day awake, making it easier to sleep on board once cabin lights dim.
During the Flight
Drink considerably more water than you normally would, roughly double your usual intake, since cabin air is dry and dehydration makes every jet lag symptom worse. Avoid alcohol and limit caffeine, both of which disrupt the sleep you’re trying to get on board.
Resist the urge to nap heavily during the day if you land in daylight and it isn’t your destination’s normal sleep time. If you genuinely need rest, keep it to fifteen or twenty minutes rather than a full sleep cycle, which can make it harder to sleep properly once night falls locally.
After You Land
Light exposure is the single most powerful tool for resetting your body clock, but timing matters. If you land in the morning after an overnight eastbound flight, avoid bright light for the first couple of hours, since it can push your body clock in the wrong direction, then seek out sunlight later in the day instead.
Set your watch to local time as soon as you land and commit to it fully. If it’s morning locally, eat breakfast and get moving, even if your body insists it’s the middle of the night. This mental commitment genuinely speeds up adjustment more than most people expect.
Who Feels Jet Lag Worst
Frequent flyers, older travellers, and anyone crossing five or more time zones tend to feel jet lag most strongly. If you’re travelling with older family members on a long-haul trip, building in a quieter first day or two at your destination, rather than diving straight into a packed itinerary, makes a genuine difference to how the rest of the trip feels.
Frequently Asked Questions
Does jet lag get worse the longer the flight is?
Not necessarily. Jet lag depends on how many time zones you cross, not flight duration. A long flight to South Africa causes little jet lag, while a shorter flight to the Gulf or Asia can cause considerably more.
Is it harder to adjust flying east or west?
Flying east is generally harder, since it compresses your day and forces you to sleep earlier than your body wants to. Flying west, which lengthens your day, is usually easier to adjust to.
Should I sleep on the plane to avoid jet lag?
It depends on your arrival time. If you’ll land at your destination’s night time, sleeping on board helps. If you’ll land in the morning, try to stay awake instead and save sleep for that first local night.
Do jet lag apps actually help?
Apps that build a personalised light, sleep and caffeine schedule based on your specific flight can genuinely simplify the planning, particularly for long-haul trips crossing five or more time zones.
Planning a long-haul trip and want help choosing flight times that minimise jet lag? See our comparison of travel agent vs booking online, and check our guide to the best time to book flights for cheaper long-haul fares.
How long does jet lag usually last?
For most people, the worst of jet lag eases within a few days, although a full adjustment often takes roughly a day for each time zone crossed. Treat that figure as a rule of thumb rather than a promise, because sleep before the trip, your age and how much daylight you get on arrival all change the pace, and eastward trips usually sit at the slower end of the range. If you are still struggling to sleep properly a week after a long-haul flight, speak to a pharmacist or your GP for advice.
Do sleeping tablets or melatonin help with jet lag?
The evidence is mixed, and the rules differ by country: melatonin is sold over the counter in some destinations but is prescription-only in the UK, while sleeping tablets can leave you groggy on arrival and may not be suitable alongside alcohol or certain medicines. This guide does not recommend for or against either option. If you are considering anything to help you sleep when you travel, speak to a pharmacist or your GP first, especially if you take other medication or you are travelling with children.
Jet Lag by Flight Length: Short, Medium and Long Haul
Not every flight deserves the same plan. Short-haul trips within Europe usually involve a time difference of no more than an hour or two, so they rarely cause true jet lag at all — tiredness after an early start or a late landing is usually simple travel fatigue, and a normal night’s sleep normally puts it right. Medium-haul flights, such as those from the UK to the eastern Mediterranean, the Middle East or the US East Coast, cross enough time zones for your body clock to notice, and a day or two of mild disorientation is common.
Long-haul is where jet lag becomes a real factor, and direction matters as much as distance. Travelling east shortens your day and asks you to fall asleep before your body feels ready, which is why eastward journeys are usually harder than westward ones of a similar length. As a rough rule of thumb — and it is only a rule of thumb — allow about a day of adjustment for each time zone crossed, so a trip to East Asia or Australia deserves a gentler first few days than a trip across the Atlantic. Timing shapes shorter trips too: our season-by-season guide to the best time to visit Croatia shows how much difference choosing the right week can make, even within Europe.
Jet Lag With Children and Older Travellers
Children often adjust faster than adults expect, but only if the adults protect their sleep. Keep naps short and timed to the local clock rather than letting a child sleep through the afternoon and be wide awake at midnight, and get everyone outside into daylight early in the day, which anchors the new routine far better than a dark hotel room. Hydration matters even more for children, who may not say they are thirsty during a flight, so offer water little and often rather than waiting to be asked.
Older travellers often feel jet lag more strongly and for longer, so build in a quieter first day or two, avoid demanding activities straight after landing, and keep regular medicines in your hand luggage in case of delays. If you are travelling as a family across the generations, our smart travel packing tips and hacks will help you organise the small things — chargers, snacks, spare clothes and documents — that make the first day at your destination much calmer. And if anyone in the group has a health condition or takes regular medication, check with a pharmacist or a GP before you travel about timing doses across time zones.
