Jet lag on a 24-hour layover: home time or local time?

On a short layover your body clock has no time to move. What the CDC and NHS say about staying on home time, light, naps and caffeine, plus fatigue rules.

On a 24-hour layover your body clock has no time to move. The CDC's Yellow Book, its health guide for international travellers, says that for short trips, for example under two days, you should avoid adapting to the new time zone. The NHS gives similar advice for trips of two to three days: you could try not changing your eating and sleeping times, so you do not have to shift again when you get home.

Many crew follow that rule and stay on home time. The habits below make it easier.

Sleep when your body clock expects it

Home time can mean sleeping in daylight in a noisy city. The NHS says you may find it easier to sleep in a room that is quiet, dark and cool, and suggests closing the curtains all the way to keep the room dark. Silence your phone before you lie down, and set an alarm for the time you want to be up.

Use light on purpose

Light is the main signal your body clock reads. The CDC says bright light in the morning moves the clock earlier and light in the evening moves it later, and that avoiding light at the wrong time is part of the plan. On home time you are trying not to move the clock, so check what time your body believes it is before you spend time in bright sun.

On a longer stay the picture changes. The CDC says westward travel is easier to adapt to than eastward travel, and the NHS says natural light in the daytime helps your body clock adjust.

Nap short

The CDC says short daytime naps of 20 to 30 minutes can help sustain alertness during the local day, while longer naps make it harder to sleep at night. Set an alarm before you close your eyes.

Watch caffeine and alcohol

The CDC advises stopping caffeine about six hours before bedtime. It also says alcohol and caffeine can both cause dehydration, which can make jet lag worse, and it suggests drinking water and avoiding excess alcohol. The NHS says too much caffeine or alcohol can make jet lag worse.

Ask your doctor, and check your company's rules, before you take melatonin or any sleeping aid. The CDC notes that melatonin taken at the wrong time can make things worse, and that the US Food and Drug Administration does not regulate it.

Fatigue rules come first

Your company's fatigue rules set your minimum rest and the hours you can be called. These tips work inside those rules. If you are too tired to operate, tell your company before you report, following its fitness-for-duty procedures. CASA, Australia's aviation safety regulator, explains pilot obligations for managing fatigue on its fatigue management pages.

See a doctor if poor sleep carries on for weeks after you get home.

Make the awake hours count

A layover leaves you awake at odd hours. Our guide to planning a short layover covers how to use that gap, and eating when your body clock is off covers meals at odd hours. If you wake at 3am with nothing open, our guide on late-night food after a late arrival helps.

On Chocks lists the spots other crew recommend and has an Open now filter. Use it when your hunger and the local clock disagree.