Sleep

Red-eyes and your body clock: a practical guide for crews and passengers

October 20, 20268 min readFor pilots and passengers

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In this article

Why the middle of the night is different
Before a night duty: sleep late, then nap
During the night: caffeine and light
Breaks in flight
Several nights in a row
After landing: recovering well
A note on melatonin
For passengers
How LogAloft helps

A red-eye asks you to be awake, and for crews to be sharp, through the hours your body has set aside for sleep. You can't move your body clock for a single night. What you can do is arrive at the flight with as little sleep debt as possible, spend the night with the few tools that work, and recover without wrecking the next night too. This guide covers that, for crews working the flight and passengers riding it.

Two other articles go deeper on parts of it: Rest is not sleep on rest periods and what a break in flight is worth, and Jet lag east and west on shifting the clock across time zones.

Why the middle of the night is different

How alert you are at any moment depends on how long you've been awake and on where you are in your body's daily cycle. In the small hours both work against you.

The FAA defines the window of circadian low (WOCL) as 02:00 to 05:59 during a physiological night (14 CFR 117.3), in the time zone your body is used to. EASA uses the same hours in ORO.FTL.105. The FAA's advisory circular on fitness for duty, AC 117-3, calls it the time "when physiological sleepiness is greatest and performance capabilities are lowest," and notes a secondary, milder low in the afternoon, roughly 15:00 to 17:00 body-clock time.

Time awake adds to it. The same circular says most adults keep normal alertness for about the first 16 hours awake and then begin to slow. On a typical red-eye, a crew member who got up at 07:00 home time and reports at 21:00 home time crosses 16 hours awake around 23:00 home time, before the airplane is anywhere near the WOCL.

So the first lever is an obvious one that often gets skipped. Cut the hours awake before the night starts.

Before a night duty: sleep late, then nap

Sleep in that morning. On the day of a night trip, skip the alarm if you can and sleep as long as your body lets you. Each extra hour in bed that morning is one hour fewer awake by 04:00 home time.

Nap in the afternoon. A planned nap before a night duty is a recognized fatigue countermeasure in aviation (Wingelaar-Jagt and colleagues, 2021), and AC 117-3 points out that a pilot reporting mid or late evening without a nap is more exposed to fatigue than one who took one. Two details make the nap work:

Timing. Sleep comes more easily in the afternoon dip than in the early evening. In a classic analysis by Strogatz, Kronauer and Czeisler, people rarely fell asleep in a zone about 1 to 3 hours before their habitual bedtime, when the body clock most resists sleep. For someone who usually goes to bed at 23:00 home time, a nap at 14:00 is more likely to come than one at 20:00.
An alarm and a buffer. Waking from deep sleep leaves you groggy for a while, an effect called sleep inertia. End the nap well before you need to be sharp, and set an alarm.

LogAloft's rest plan works the same way. It leaves the morning without an alarm and then puts in a nap of one sleep cycle, about 90 minutes, ending half an hour before you start getting ready, which is about two hours before the report.

During the night: caffeine and light

Caffeine

Caffeine helps most when your body is fighting sleep, and small, repeated amounts work well. In a laboratory study by Wyatt and colleagues (2004), about 0.3 mg per kilogram an hour (roughly 20 to 25 mg an hour for a 70 to 80 kg adult) held off the decline in performance, especially at the body's low point.

The cost comes later. Drake and colleagues (2013) gave 400 mg of caffeine at bedtime, 3 hours before it, or 6 hours before it. Even at 6 hours, it reduced sleep by more than an hour. On a red-eye that lands at 06:00 local time with sleep planned for 08:00 local, caffeine after about 02:00 local is already inside that window.

For a crew member, alertness on the approach comes first, so the rule needs bending. One way to do it:

most of your caffeine early in the duty, before the WOCL;
small amounts after that if you need them, not a large cup late;
nothing in the last couple of hours before landing unless you're struggling, and then accept a lighter sleep afterward.

Passengers who want to sleep on board should skip caffeine after the evening.

Light

Bright light in the night makes you more alert, and it also tells your clock it's daytime. For a single red-eye you aren't trying to move your clock, so the light that matters most comes after landing. Morning daylight on the way home or to the hotel signals the start of the day, just when you want to sleep.

Night-shift research uses dark sunglasses for exactly this. In a study by Smith, Fogg and Eastman (2009), night workers wore dark sunglasses outdoors and slept in dark bedrooms, as part of a plan that let them sleep nearly all of the time they had in bed. On a red-eye that crosses several time zones, the rules change, because your body's morning falls at a different local hour. Jet lag east and west explains when daylight helps and when it pushes the wrong way.

Breaks in flight

On augmented crews the break is your best chance at sleep during the night, but it gives less than its length. In one long-haul study, pilots slept about 3.3 hours in a 7-hour break, as Rest is not sleep describes. In the same study, breaks taken early in the flight gave less sleep than later ones, which fits the evening zone when the body clock resists sleep. Plan the minutes after waking as well, and give yourself a few of them before you take over a task that needs full attention.

Several nights in a row

The rules treat runs of night duties as a fatigue risk in their own right.

Rule	What it says
14 CFR 117.27	At most 3 consecutive flight duty periods that infringe on the WOCL, or up to 5 if each includes a rest opportunity of at least 2 hours in a suitable accommodation
EASA CS FTL.1.205(a)	For consecutive night duties, at most 4 sectors per duty, and fatigue risk management for night duties of more than 10 hours

After landing: recovering well

The aim after a red-eye is to repay some of the night without ruining the next one.

Keep the first sleep limited. A long sleep through the morning feels good and leaves you wide awake at midnight. One or two sleep cycles (90 minutes or 3 hours) with an alarm, then up, outside in daylight if you can, and to bed earlier than usual that night. The short sleep pays off part of the debt and leaves enough sleep pressure for a full night, and it is what LogAloft's rest plan suggests after a night flight. When the night ahead falls in your body's day, as after a big shift east, keep it to one cycle.

Expect recovery to take more than one night. AC 117-3 notes that it takes less sleep to repay a debt than the hours you lost, but after several short nights, full recovery "may require several days of 9 hours or more sleep per day."

Get home safely. If you are fighting to stay awake behind the wheel, take a ride or nap first.

A note on melatonin

Melatonin is popular for red-eyes and for sleeping after them, and it comes with cautions.

Quality varies. In the US, melatonin is sold as a dietary supplement and regulated less strictly than a drug. A 2017 study described by the NIH's National Center for Complementary and Integrative Health found that for most of 31 products the amount of melatonin didn't match the label.
Timing matters more than dose. Taken at the wrong point in your body's day, it can move your clock the wrong way. Jet lag east and west covers the timing.
Pregnancy. The same NIH page notes a lack of research on its safety in pregnancy and while breastfeeding.
Pilots. The FAA's guidance on sleep aids allows occasional use for circadian disruption in airline flying and requires a wait of at least 5 times the drug's maximum elimination half-life before pilot duties. LogAloft's own margin is stricter, and its plans never put melatonin within 8 hours before a flight.

Ask your doctor, and if you're a pilot your aviation medical examiner, before using it.

For passengers

Most of the crew advice carries over. Sleep in on the morning of the flight, nap in the afternoon if you can, and skip caffeine in the evening. On board, an eye mask and earplugs help. After landing, keep the first sleep short and go to bed early that night. If you land somewhere several time zones away, follow the light advice for that direction rather than the usual "get some sun."

How LogAloft helps

In LogAloft, every layover before a night flight gets a rest plan with the morning sleep-in and the afternoon nap, and the Breaks planner for long legs shades your window of circadian low so you can place the rest periods. When three or more reports in the next 30 days fall in your body's night, a heads-up on Today flags them before you bid. The plans are for planning, not medical advice, and they don't replace your company's fatigue policy.

For how LogAloft turns these ideas into a plan for each layover, see How LogAloft plans your rest.

Sources

This is information, not medical advice. For questions about your own health or a pregnancy, talk to your doctor or aviation medical examiner.