The evening departure from JFK to Heathrow is a staple of transatlantic business travel, and it is built around a cruel piece of arithmetic. The aircraft lands around breakfast in London, while a body still keeping New York time believes it is two or three in the morning, the hour when alertness reaches its lowest point and a meeting at nine feels like a test of endurance.
The good news is that jet lag responds to a small set of levers with solid evidence behind them. Shifting your sleep toward the destination in the days before departure, timing bright light to the direction of travel and taking a low dose of melatonin near the destination bedtime all move the body clock faster than waiting it out, while caffeine and short-acting sleep aids manage the symptoms in between.
What the evidence does not support is the idea that a better seat solves the problem. A lie-flat bed improves the odds of sleeping on board, but the misalignment between the internal clock and local time travels with every passenger, whatever the cabin.
Why Eastbound Hurts More Than Westbound
The CDC Yellow Book chapter on jet lag disorder, written for the 2026 edition by Samantha M. Riedy and Scott G. Williams, puts numbers on what frequent flyers already feel. It states that westward travel is easier to adapt to than eastward travel, with an average adaptation rate of 1.5 hours per day after flying west and 1 hour per day after flying east.
The reason lies in the clock itself. A landmark 1999 study in Science led by Charles Czeisler of Harvard, conducted with NASA support, found that the intrinsic period of the human circadian pacemaker averages 24.18 hours. A clock that naturally runs a little long finds it easier to stretch the day, as a flight to Los Angeles or Tokyo demands, than to shorten it, as a flight to London, Paris or Rome requires.
Applied to a typical trip, the figures are sobering. New York to London is a five-hour shift, which at an hour a day means close to five days before the body fully lines up with local time, while a traveler flying from New York to Los Angeles faces a three-hour shift that clears in about two days.
The Three Days Before Departure
The most underused tool is the calendar, and pre-flight schedule shifting costs nothing. The CDC recommends shifting sleep 1 hour earlier each day for eastward travel, or 1 hour later for westward travel, in the 2 to 3 days before the trip, which can erase much of a five-hour gap before the aircraft leaves the gate.
Researchers at Rush University Medical Center in Chicago tested a more aggressive version. In a 2006 study in the Journal of Clinical Endocrinology and Metabolism, Victoria Revell, Helen Burgess, Charmane Eastman and colleagues combined bright light on waking, delivered in four 30-minute pulses of about 5,000 lux, with afternoon melatonin over three days. Participants taking 0.5 mg of melatonin advanced their rhythms by 2.5 hours, against 1.7 hours on placebo, and the authors concluded the treatment advanced circadian rhythms almost an hour a day while producing very little circadian misalignment.
For most travelers the practical version is simple. Before an eastbound trip, go to bed and wake an hour earlier for each of the last three nights, open the curtains or step outside immediately after waking, and keep evenings dim, so that by departure day the body is already living partway on London time.
Light Is the Strongest Signal
The CDC states that the optimal timing for light exposure depends on the direction of travel and the number of time zones crossed. After an eastbound flight, its guidance is to get bright light in the early morning, opening the window shade and skipping dark sunglasses. After a westbound flight, the advice reverses, with travelers told to avoid bright early-morning light by closing the shade and wearing dark sunglasses.
The American Academy of Sleep Medicine's clinical guideline on circadian rhythm disorders reaches the same conclusion, listing the combination of morning bright light and shifting the sleep schedule one hour earlier each day as an option for eastward travel. On arrival in London that means a morning walk rather than a nap in a darkened hotel room, and a firm bedtime that evening even if the first night feels early.
Melatonin, at a lower dose than the bottle suggests
Melatonin for jet lag carries the strongest rating of any jet lag treatment in the AASM guideline, which designates its use at the appropriate time as a standard for reducing symptoms and improving sleep. A Cochrane review by Andrew Herxheimer and Keith Petrie, which included ten trials, found that daily doses between 0.5 and 5 mg were similarly effective, with the benefit clearest on flights crossing five or more time zones, particularly eastward, when taken close to the destination bedtime of 10 p.m. to midnight.
The current CDC guidance is more conservative on dose, noting that 0.5 to 1 mg is often enough to produce a circadian shift and recommending against high-dose melatonin above 5 mg. The Cochrane authors also flagged case reports suggesting that people with epilepsy and patients taking warfarin may come to harm from melatonin, which makes a conversation with a physician worthwhile before packing a bottle.
Sleep aids and caffeine
The AASM lists short-term use of a benzodiazepine receptor agonist hypnotic, a class that includes zolpidem and eszopiclone, as an option for jet lag insomnia, and the CDC advises that each drug's half-life and possible side effects be weighed before use, warning against sedatives with long half-lives. Taking one on board is a decision for a doctor rather than a cabin crew.
The CDC's chart suggests 200 mg of caffeine every four hours during daylight at the destination, roughly two cups of brewed coffee each time, and notes that caffeine has a half-life of about five hours, so the last cup should come early enough in the afternoon that it does not sabotage the first real night's sleep.
What the Aircraft Contributes
Cabin design plays a supporting role. Federal certification rules, under 14 CFR 25.841, require pressurized cabins to maintain a cabin pressure altitude of not more than 8,000 feet in normal operation, and that ceiling has long defined the long-haul experience.
Composite airframes changed the number. Boeing says the 787 maintains cabin pressurization at an altitude of 6,000 feet and pairs it with higher humidity and lighting that shifts gradually to mimic sunrise and sunset, while Airbus advertises the same 6,000-foot cabin altitude on the A350 along with LED ambient lighting capable of 16.7 million colors. Both manufacturers present these features as reducing fatigue and jet lag, and travelers should read those claims as the marketing they are, since neither changes the speed at which a body clock shifts.
Qantas has gone furthest in testing the idea. In 2019 it flew three Project Sunrise research flights from New York and London to Sydney with researchers from the University of Sydney's Charles Perkins Centre, who monitored 23 volunteer passengers wearing tracking devices while adjusting cabin lighting, meal timing and movement. The university has described the initial findings as unpublished, so they point in a direction rather than prove a result, and the same Sydney ambitions now drive the airline's 22-hour A350-1000ULR program.
A Plan for the Two Classic Trips
New York to London or Paris, overnight
Start three nights out, moving bedtime and wake time an hour earlier each night and getting outdoor light right after waking. On board, eat early, skip the full dinner service if it runs late, set your watch to London time and try to sleep as soon as the cabin lights dim. On arrival, get outside in the morning, hold off on caffeine after early afternoon and, if your doctor agrees, take 0.5 to 1 mg of melatonin near a 10 p.m. local bedtime for the first few nights.
The West Coast or New York to Tokyo, Seoul or Singapore
Westbound trips across many time zones are kinder to the clock, but they still benefit from planning. Shift bedtime an hour later for the last two or three nights, avoid bright early-morning light for the first days after landing, seek out late-afternoon light instead, and resist the urge to sleep in the middle of the local afternoon, which delays adaptation further.
Holiday travelers face the hardest version of all of this, since the peak dates we covered in our guide to booking Thanksgiving and Christmas flights often mean short trips with little time to adjust. On a four-day visit to London, some frequent flyers stay partly on home time on purpose, booking afternoon meetings and late dinners, which is a reasonable choice when the clock would barely finish shifting before the return flight.
