Aircraft noise and sleep: how many night flights is too many?

Sleep is the effect of aircraft noise that researchers can measure most directly, and the one where the number of planes matters more than the average. The research does not name a number of night flights that is safe. It does show how the disturbance builds up: with each loud plane, with how loud it is inside the bedroom, and with the time of night.

The short answer

These are the most useful markers from the research:

• The WHO's night level. The World Health Organization recommends keeping aircraft noise below 40 dB Lnight, the average from 23:00 to 07:00. Even at that level, about 11% of people reported being highly sleep-disturbed.
• The number of loud planes. In the UK's ANNE survey, 1 in 10 people were highly sleep-disturbed where somewhere between 5 and 20 planes on an average summer night were louder than 60 dB outside.
• A limit on awakenings. German sleep researchers proposed that aircraft should cause, on average, less than one extra awakening per night, and that planes louder than 65 dB inside the bedroom should be avoided.
• The time of night. In the ANNE survey, people reported disturbed sleep at the lowest noise levels between 03:00 and 06:00.

What one plane does to a sleeping person

Some of the most detailed evidence comes from the German Aerospace Center (DLR). In 2001 and 2002 it recorded the sleep of 64 people living near Cologne-Bonn, one of Germany's busiest airports for night cargo, for nine nights each, with electrodes measuring brain activity and microphones inside and outside the bedroom. More than 10,000 aircraft noise events went into the analysis.

Everyone wakes briefly many times a night: about 24 times on average, in the DLR's data. Planes add to that. The chance of an extra awakening started to rise when a plane's peak level inside the bedroom passed about 33 dB, only about 6 dB above the room's background. A plane just above that threshold woke about 2 people in 1,000, and the effect grew steadily with loudness. Pooling studies of this kind, the WHO's review found the odds of waking about 35% higher for every 10 dB louder inside, and rated that evidence moderate.

Loudness also changes how long you stay awake. In the DLR's laboratory study, awakenings caused by planes of 65 dB or less inside were about as short as natural ones, while planes of 70 dB or more caused longer ones, the kind you are more likely to remember in the morning. Nights with aircraft noise had about 9 minutes less deep sleep than quiet nights, although total sleep time did not fall significantly.

The body reacts even without a full awakening. In the HYENA study, which measured blood pressure every 15 minutes in 140 sleeping people near four European airports, it was on average 6 to 7 mmHg higher in the intervals when a plane was recorded.

What reaches the bedroom depends on the window. The WHO puts the difference between outdoor and indoor levels at about 10 dB with the window open, 15 dB with it tilted and 25 dB with it closed. So a plane at 80 dB outside is about 65 dB inside a room with a tilted window.

Why the number of flights matters more than the average

Official night-time figures such as Lnight are averages. The WHO itself warns that averages may hide effects such as awakenings, and that counts of loud events may describe them better.

More planes mean more awakenings, though not in proportion. In the DLR's laboratory work, each plane was less likely to wake people as the number in a night went up. The DLR's proposal for Leipzig/Halle, a night cargo hub, was framed in awakenings rather than an average. Protection zones were drawn so that outside them aircraft should cause less than one extra awakening per night on average, and planes above 80 dB outside, about 65 dB inside with a tilted window, should occur less than once a night. Germany's Federal Administrative Court upheld the concept in 2006.

The same average can also describe very different nights. Where the runway direction changes with the wind, a street can have a steady few planes every night, or many on some nights and none on others.

What surveys find: the WHO level and the UK's ANNE study

Surveys ask people directly how much aircraft noise disturbs their sleep. The WHO's review, based on six surveys of 6,371 people, found:

The WHO wanted no more than 3% of people highly sleep-disturbed, but had no reliable data below 40 dB, so it set its level there and said it may not fully protect health. How that level was chosen is in our guide to the WHO guidelines. An update of the review in 2022, with 11 more studies, agreed closely at 40 dB but found more disturbance from aircraft at high levels than the WHO had estimated.

The UK's Aviation Night Noise Effects (ANNE) study, published by the Department for Transport in June 2026, surveyed 4,183 people near eight UK airports, including Heathrow, Gatwick, Manchester and Stansted, between October 2022 and January 2023. Very few people were highly sleep-disturbed below 36 dB LAeq,8h, the UK's summer-night average. One in ten was at 44 dB, just under the 45 dB the UK treats as the level where adverse effects begin, and around 20-28% were at 49-60 dB. A second part of the study, measuring sleep with sensors, is expected later in 2026.

In the US, the FAA's main measure, DNL, handles night flights by adding 10 dB to them, and the FAA has commissioned a national field study of aircraft noise and awakenings. A long-running study of US nurses found that those exposed to 45 dB Lnight or more had 23% higher odds of sleeping less than seven hours.

Early-morning flights: why 4 a.m. matters more than midnight

ANNE also looked hour by hour, and found that the level at which 1 person in 10 was highly sleep-disturbed varied a lot through the night:

Part of the difference is simply that fewer people are trying to sleep at 22:00 or 06:30. But the authors also suggest that early in the night people are tired and fall back asleep easily, while a plane at 4 a.m. wakes someone who has already slept for several hours and may not get back to sleep. The DLR reached a similar view, and for Leipzig/Halle it treated planes in the second half of the night as if they were 1.4 dB louder, to protect people's ability to fall asleep again.

A night ban helps, but the hours either side of it still matter. At Frankfurt, which banned flights from 23:00 to 05:00 in October 2011, the NORAH study found that residents woke less often in 2012, as fewer planes were heard in their bedrooms. But people who went to bed around 22:00 and got up around 06:00 woke less than those who slept an hour later, because the later sleepers were woken more often by early-morning flights. And participants said they felt somewhat more tired in the mornings than the year before, at the same noise levels.

Check when the first arrivals come. At Heathrow, for example, scheduled early-morning flights may land from 04:30, and about 80% of its night flights land between 04:30 and 06:00, about 16 a day.

Does broken sleep harm health?

Tiredness is the obvious cost. Links with longer-term health are less certain. In the HYENA study, each 10 dB of night-time aircraft noise went with 14% higher odds of high blood pressure, and a study near Zurich found deaths from cardiovascular disease at night were more likely when aircraft noise in the two hours before had averaged above 50 dB rather than below 20 dB. The WHO rates the evidence on heart disease as very low quality. The full picture is in is living near an airport bad for your health?

What to check for a home

Before you buy or rent, look at the nights, not only the days:

• Loud planes between 23:00 and 07:00, on an average night and on the busiest nights. The count matters more than the total number of flights at the airport.
• When the first ones arrive. Planes between 03:00 and 06:00 disturb people at the lowest levels.
• Which runway direction brings night flights over the home, and how often the airport uses it.
• The airport's night rules. Curfews, quotas and bans differ a lot between airports; see how night flight rules work.
• Which way the bedrooms face, and whether you could sleep with the windows shut.

If you already live under a flight path, sleeping under a flight path covers earplugs, white noise and bedroom tips.