Jet Lag Tips for Flying from London to New York

Understanding Westbound Jet Lag: Phase Delay Explained

The internal clock that governs alertness, hunger and sleep runs on a cycle slightly longer than 24 hours. It prefers to drift later. That is why staying up late feels easier than waking up early. Flying west, from London to New York, pushes you into a time zone that is behind your internal clock. New York is five hours behind London in standard time (and during most of the year, though the UK and US clock-change dates differ, which can shrink the gap to four hours for a few weeks each spring and autumn).

This mismatch is called a phase delay. Your body wants to go to sleep and wake up later than the local time demands. You will not struggle to get to sleep at 23:00 New York time. You will struggle to stay asleep past 05:00 New York time, because your London body clock thinks it is 10:00 and time to get up.

Why London to New York Causes Difficulty Waking Up

The core problem is the early part of the day. In London, your natural wake time might be 07:00. In New York, that same biological signal fires at 02:00 local time. You wake up, or wake partially, in the middle of the New York night. The result is grogginess, poor performance in early meetings, and a crash by mid-afternoon.

The standard workday overlap between London and New York is 13:00-17:00 London time, which is 08:00-12:00 New York time. If you cannot function during that window, you miss the only time both cities are fully working.

Pre-Flight Preparation: Shifting Your Schedule from London

Most jet lag advice tells you to shift gradually in the days before travel. That is correct, but the direction matters. For a westbound trip, you need to delay your schedule, not advance it.

What to do: For two or three days before your flight, go to bed 30-60 minutes later than usual and wake up 30-60 minutes later. If you normally sleep 23:00-07:00 London time, aim for 00:00-08:00. Do this by staying in brighter light in the evening and dimming lights earlier in the day.

What goes wrong: People try to wake up earlier before a westbound flight. That is the eastbound strategy. It makes the phase delay worse. You arrive in New York even more misaligned.

Light Exposure Strategy: Seek Evening Light, Avoid Early Light

Light is the strongest signal for resetting your body clock. For a phase delay, you want to push your clock later. That means you need bright light in the late afternoon and evening at your destination, and you need to avoid bright light in the early part of the day.

On arrival in New York:

• Avoid light before 09:00: From around 05:00 to 09:00 New York time, wear sunglasses or stay indoors if you are awake. If you are outside, keep your eyes down and wear wrap-around sunglasses. This is the hardest part of the strategy, especially if you wake naturally at 04:00 or 05:00 New York time. Stay in dim light until at least 08:00.
• Seek evening light: From 15:00 until sunset, get as much bright light as possible. Go for a walk, sit by a window, or eat outside. The goal is to tell your body clock that evening is still daytime, which delays your internal bedtime.

What goes wrong: The instinct on arrival is to go outside and soak up the early sun to “reset.” That light tells your body it is daytime in New York, which advances your clock. You need a delay, not an advance. Early light makes you wake up even earlier the next day.

In-Flight Tips: Hydration, Sleep, and Meal Timing

The flight from London to New York is roughly seven to eight hours. It departs London in the late morning or early afternoon and arrives in New York in the mid-to-late afternoon local time.

Sleep: Sleep when it is dark outside the window. If the flight departs at 11:00 London time, that is 06:00 New York time. The cabin lights will be on. Wear an eye mask and try to sleep for the first two to three hours. Wake up with about three hours to go, eat the meal, and then stay awake until landing.

Hydration: Drink water. Avoid alcohol and caffeine. The cabin humidity is below 20 per cent. Dehydration worsens jet lag symptoms.

Meal timing: Eat the meal that is served. Do not skip it. Your body uses meal timing as a secondary time cue. Eating at the time the airline serves food (which is roughly aligned with destination time) helps shift your clock.

What goes wrong: Watching movies with the cabin lights on and then sleeping through the arrival meal. You arrive having eaten nothing for eight hours and with no light exposure at the right time.

Post-Arrival: The First 48 Hours in New York

The first two days determine how quickly you adjust.

Day 1: Follow the light rules strictly. Avoid light before 09:00. Get evening light. Eat meals at New York meal times, not London meal times. If you are hungry at 03:00 New York time (08:00 London time), eat a small snack, not a full breakfast. Wait until 07:00 or 08:00 New York time for breakfast.

Day 2: Your body clock will have shifted roughly one to two hours. You can start allowing a little light earlier in the day, but still keep the main light exposure in the afternoon and evening. By the evening of day two, you should be able to sleep until 06:00 or 07:00 New York time.

What goes wrong: People nap in the afternoon. An afternoon nap on day one reduces the drive to sleep at night and resets your clock to London time. If you must nap, keep it under 30 minutes and before 14:00.

How the 5-Hour (or 4-Hour) Difference Affects Recovery

The UK and US change clocks on different dates. The UK moves to BST (UTC+1) on the last Sunday of March. The US moves to EDT (UTC-4) on the second Sunday of March. For the two to three weeks in between, New York is only four hours behind London instead of five. The same gap appears in autumn: the US goes back to EST (UTC-5) on the first Sunday of November, while the UK stays on BST until the last Sunday of October.

During those weeks, the jet lag is slightly milder, a four-hour shift is easier than a five-hour shift, but the strategy is identical. The light timing advice does not change. The workday overlap shifts by one hour, so check the current offset on the London vs New York time page before scheduling calls.

Who Should Ignore the Default Advice

The default jet lag advice, “get early sun, avoid evening light”, works for eastbound travel (London to Dubai, Singapore, or Tokyo). It is wrong for westbound travel.

Anyone flying from London to the Americas should ignore that advice. Specifically, if you are a business traveller who needs to be functional for the 08:00-12:00 New York workday overlap, or if you are travelling for an early event (conference, meeting, family gathering), follow the phase delay plan. Evening light. Avoid early light. Delay your schedule before you fly.

If you are on holiday and do not care what time you wake up, none of this matters. Sleep when you are tired. But if you need to be awake and alert for the first half of the New York day, the evening light strategy is the one that works.