Jet Lag Flying West: Why the Easy Direction Still Gets You

Flying west is supposed to be the easy direction. Everyone says so, and on paper it is true: your body clock runs slightly longer than 24 hours, so stretching the day is more natural than shortening it. Yet plenty of people land in Los Angeles from London feeling fine on day one and then fall apart on day three, waking at 3 am wide eyed and useless by dinner.

That pattern is not bad luck. It is what happens when you treat westward travel as the direction that takes care of itself. It does not. It just fails differently.

Here is how I handle it, and why the mistakes people make going west are almost the opposite of the ones they make going east.

Why west feels easier and then bites

Your internal clock does not run on exactly 24 hours. Left alone in a cave with no light cues, most people drift to something closer to 24.2. That small surplus is why staying up late is easy and going to bed early is hard, and it is why phase delaying, which is what westward travel asks of you, is the direction your body already leans.

So the first day usually goes well. You land in the afternoon, you are tired in a pleasant way, you stay up until a reasonable local bedtime and sleep hard.

The trouble starts on night two and three. You went to bed at local 10 pm, but your body still thinks it is the small hours, and after the pressure from a long travel day has been discharged, it wakes you at what it considers morning. Now you are awake at 3 am local, you nap in the afternoon to compensate, and the nap pushes your clock right back where it started. Repeat that for a few days and you never actually adapt. You just oscillate.

The fix is to stop the drift on the first two days rather than react to it on the fourth.

The rule for going west

Going east, the job is to advance your clock, which means morning light and no evening light. Going west, everything flips. The job is to delay your clock, which means evening light and protected mornings.

That single sentence is most of the protocol. The details are just how to execute it without wrecking yourself.

What I actually do

Before I leave, I shift a little. Two or three nights before a westward flight I go to bed 45 minutes later than usual and sleep in the same amount if I can. Even one hour of pre shift takes a day off the arrival. Do not try to do the whole thing in advance. A few hours of head start is realistic, a five hour shift is not.

On the plane, I use local destination time from the moment I board. Watch changes, phone changes, meals get planned around the new day. If it is early afternoon at the destination, I stay awake, work, and eat. If a long flight crosses what will be night at the destination, I sleep then and not before.

I do not sleep the whole flight going west. This is the most common error. A westward flight often departs in the morning and lands in the afternoon, so sleeping through it puts you on the ground with no sleep pressure at all, staring at the ceiling at 11 pm local and then crashing at 4 am. Rest, do not sleep, unless it is genuinely night where you are going.

I get outdoor light in the late afternoon and early evening on arrival. This is the active ingredient. Bright light in the hours before your usual bedtime pushes your clock later, which is exactly what you want. A walk between 4 pm and 7 pm local does more than any supplement. If it is winter or overcast, get outside anyway, because even a dull day outdoors beats indoor lighting by a wide margin.

I protect the early morning from light. If you wake at 4 am local and turn on lamps or step outside, you are telling your clock that this is morning, and it will keep waking you there. Blackout curtains, an eye mask, and no bright screens if you do wake. When I want to be deliberate about light exposure at the right times I use VivaRays glasses, because the point is not blocking everything all the time. It is blocking the wrong light at the wrong hour and getting the right light when it counts.

I let bedtime come late and I hold the wake time. Going west, I would rather go to bed slightly late and get up at a fixed local time than go to bed early and be up at 3 am. Bedtime is the flexible end. Wake time is the anchor.

Caffeine early, and then done. Coffee in the local morning is useful. Coffee after about noon on the first days is how you end up awake at midnight with your clock unchanged. If I need to get through a late afternoon slump, I walk outside instead. That is doing double duty, because the light is the treatment.

Naps are a tool with a strict limit. If I have to nap, it is 20 minutes and it is before 3 pm local. Anything longer or later dumps the sleep pressure I need to fall asleep at local bedtime.

Melatonin plays a smaller role going west. Going east, a small dose in the destination evening helps advance the clock. Going west, the direction you want is delay, and the timing that would help is a small dose in the early morning hours, which is awkward and easy to get wrong. For most westward trips I skip it and lean on light and timing instead. If you do use it, small doses work better than large ones, and talk to your physician if you take other medication.

I keep the room cold. Sleeping in an unfamiliar bed in a warm hotel room is a bad combination when your clock is already fighting you. Air conditioning down, duvet off, sheet only. I wrote about why temperature matters this much in the cold room rule.

What to expect

The usual estimate is that you adapt about one and a half time zones per day going west, versus roughly one per day going east. So London to Los Angeles, eight hours, is realistically four or five days if you do nothing, and two or three if you pre shift and get the light timing right.

If your trip is shorter than three days, do not adapt at all. Stay on home time, schedule what matters for the hours that overlap with your normal waking day, and go home unshifted. Adapting and then re adapting for a two day trip costs you more than it gives.

The short version

Going west, do the opposite of what you would do going east. Shift later before you leave, stay awake on the plane unless it is night at the destination, get outside in the late afternoon, guard your mornings from light, hold your wake time steady, and keep naps short and early.

I put the full protocol for both directions, along with the light timing tables and the travel day checklist, into a free guide. You can get it at sleepbiohacker.com/jetlag.

This post is for educational purposes only and is not medical advice. Some links are affiliate links, which means I may earn a small commission at no extra cost to you. I only recommend things I use.