Runway alternation explained: why some days are quiet and others aren't

If you live under an approach to a two-runway airport, you may have noticed that the planes follow a timetable: all morning one week, all afternoon and evening the next, and on some days none at all. That is runway alternation, and once you know the pattern, you can plan around it.

What runway alternation is

An airport with two parallel runways can use one for landings and the other for take-offs. Landing planes are the most predictable part of the traffic, because they line up with the runway many kilometres out and descend along a straight line. Every house under that line hears every landing, at the same low height each time.

Alternation swaps the roles of the two runways at set times. While one runway takes the landings, the homes under the other approach get a break. Heathrow describes it as giving local communities predictable periods of relief from noise: if you were under an incoming flight path in the morning, you are unlikely to be under one in the afternoon.

It does not reduce the number of flights. It changes when each street hears them.

How it works at Heathrow

Heathrow's two runways run east to west, about 1.4 km apart. On westerly days, when planes land towards the west over London, the rules are:

• Day runs from 06:00 until the last departure, and the switch comes at 15:00. One runway takes landings until 15:00, then the other takes them until the end of the day.
• Every week the order swaps. What happened in the afternoon last week happens in the morning this week. Weeks start on Monday.
• Between 06:00 and 07:00 both runways can take landings, because it is the busiest hour for arrivals.
• The runway not taking landings takes the take-offs.

The system has been in place since the 1970s. Over the last year, each of the two westerly approaches took about half of the westerly landings.

The approach to the northern runway, called 27R, passes over Fulham, Chiswick, Kew, Isleworth and Heston. The approach to the southern runway, 27L, passes over Putney, East and North Sheen, St Margarets and Hounslow. Heathrow's programme for the next few weeks of 2026 reads:

The two approaches are only 1.4 km apart, and a large jet at around 2,000 ft is loud well to either side of its line. Homes between the two lines, or close to both, hear landings on both runways, so they get less relief than homes directly under one.

Night-time alternation at Heathrow

At night there are far fewer flights, so Heathrow can alternate both the runway and the direction. From the last departure until 06:00, it runs a four-week cycle:

1. Planes come in from the west to land on the northern runway.
2. Planes come in from the east to land on the northern runway.
3. Planes come in from the west to land on the southern runway.
4. Planes come in from the east to land on the southern runway.

Because the wind can rule out the planned direction, each week also has a back-up, which is the same runway approached from the other end. The night pattern changes on Monday mornings at 06:00, so the early hours of Monday still follow the previous week. Heathrow's night rules, including the 04:30 limit on early arrivals, are on our Heathrow page.

Why there is no alternation on easterly days

When the wind is from the east, about 30% of the time at Heathrow, alternation stops. Nearly all easterly landings use the northern runway, 95% over the last year, and the take-offs use the southern runway, all day.

This goes back to the Cranford agreement of 1952, which kept take-offs away from the village of Cranford at the eastern end of the northern runway. The government ended it in 2009, but easterly alternation needs new taxiways and a noise barrier near Longford before it can start, as well as changes to the airspace. Hillingdon Council resolved to grant planning permission for the works in December 2025, and the airspace change has a review with the Civil Aviation Authority scheduled for January 2027. Heathrow says the change would share noise more evenly: some streets that rarely hear planes on easterly days would start to, and others would hear fewer. Easterly and westerly operations explains how the two directions differ street by street.

When the pattern breaks

Even on westerly days, the schedule is a plan rather than a promise. Heathrow names the usual reasons it is not followed:

• Delays. When there is severe congestion after 07:00, Heathrow can land up to six planes an hour on the runway meant for take-offs. This is called Tactically Enhanced Arrivals Mode.
• Runway works. Maintenance is often timed to fit the alternation pattern, but not always. In 2026, planned runway works mean departures from the schedule, particularly at night.
• Weather. Strong south-westerly winds blowing across buildings in the maintenance area can affect which runway is used, and bad weather can suspend alternation.
• Emergency repairs to one of the runways.
• A change of wind. If the airport turns round to easterly, westerly alternation ends until it turns back. How and when that happens is explained in why flight paths change with the wind.

Do other airports alternate?

Alternation needs two runways that can each take landings, so an airport with a single runway cannot do it. And a weekly timetable like Heathrow's is not the only way of sharing out quiet time.

Frankfurt, which lands planes on its two outer parallel runways, has used noise respite periods since April 2015. Its night flight ban runs from 23:00 to 05:00; under the respite scheme, some residents get an extra hour, with quiet either from 22:00 to 05:00 or from 23:00 to 06:00, alternating between the two. A monitoring report by the Hessian transport ministry in 2016 found a significant reduction in the noise footprint.

Alternation is also part of the plans for a bigger Heathrow. The government's draft policy statement for a third runway, consulted on in 2026, proposes keeping runway alternation.

The limits of alternation

Alternation gives predictable breaks, but only within limits. It applies on westerly days only, which at Heathrow means about seven days in ten. It does not cover the first hour of the morning, when both runways can take landings. It can be broken by delays and works. And it helps most the homes directly under one approach, not those between the two.

How to find the schedule

• Heathrow's runway alternation programme is published each year as a PDF on its runway alternation page. It lists the landing runway before and after 15:00 for every week, and the night-time runways.
• Updates on works. Heathrow posts changes caused by runway works on its runway resurfacing page and on X as @HeathrowRunways.
• What actually happened. Heathrow's WebTrak shows recent flights with their heights. Our free flight map replays a whole day, so you can see which runway took the landings in the morning and in the afternoon.