Why Flight Direction Matters

East Is a Beast, West Is Best: Why Flight Direction Matters

Ask frequent flyers which way hurts more, and most will say east. They’re right, and the reason says a lot about how jet lag actually works.

Nothing north or south

Jet lag comes from crossing time zones, not from distance. Fly from Sydney to Singapore, or from London to Johannesburg, and you’ll arrive tired but your body clock will be roughly where it should be. That’s travel fatigue, not jet lag. What matters is how far east or west you go.

Every trip is two trips

It’s easy to think of a trip as one journey. For your body clock, it’s two. If you fly east on the way out, you fly west on the way home, and your clock has to shift one way and then the other. A short trip can mean you’re still adjusting to the destination when it’s time to come back.

Why east is harder

Flying west, the day gets longer. You stay up later than your body expects, and for most people that’s easier, because the internal clock naturally runs a little longer than 24 hours. Stretching the day works with it.

Flying east, the day gets shorter. You’re asked to fall asleep when your body thinks it’s still the afternoon and wake up when it feels like the middle of the night. That means squeezing the day, which is going against the grain.

Longer recovery going east

The practical result is that recovery takes longer after eastward travel. For the same number of time zones, you’ll generally need more days to feel normal again flying east than flying west. Sleep stays disrupted for longer, and so do the daytime fog and poor concentration. For a business traveller, that can mean arriving for an important meeting still well short of your best.

Two different mechanisms

Eastward travel needs a phase advance: your clock has to shift earlier. Westward travel needs a phase delay: your clock has to shift later. They’re not mirror images. Delaying is generally easier than advancing, so the two directions behave differently and call for different strategies.

This is also why the timing of light matters so much. Morning light helps advance the clock, which suits eastward travel, while afternoon light helps delay it, which suits westward travel. Get the timing wrong and the same sunlight can push your clock the wrong way.

The takeaway

Direction is one of the first things to look at when planning a trip. It’s why the same traveller can breeze through a flight west and struggle for days after the same distance east. Plan the outbound and the return as two separate shifts, because they are, and allow more recovery time when you’re heading east.

If you want a plan matched to your route and your own body clock, book a session with me on EveryExpert.