Everything You Need To Know About Runways

For some, they signify moments of excitement. For others, they are simply a necessary means to an end. No matter which category of traveler you fall under, there is no denying that flying as we know it would not be possible without the humble runway. Let’s take a closer look at aviation’s unsung hero.

blue-ice runway antarctica
Some runways are made of ice. Photo: Getty Images

Snow, beach, or cliff?

The International Civil Aviation Organisation defines a runway as “a defined rectangular area on a land aerodrome prepared for the landing and take-off of aircraft.” Which is a rather broad characterization.

Some are made of layers of compact snow, like the Ice Runway at McMurdo Sound, used by the US Antarctic Program. Others consist of sand, like at Barra Airport in Scotland, where planes land on a beach at low tide. Others are so short that pilots often can’t pick up enough speed to take off and have to drive the plane off of a cliff and take flight during the drop, like at Matekane Airstrip in Lesotho.

Thankfully, most airport runways come in more standard varieties than the above mentioned. However, there are, of course, big differences in lengths and construction.

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The long and the short

The world’s longest runway is located at 4,400 meters above sea level at Qamdo Bamda Airport in Tibet and measures 5,500 meters. At the other end of the scale, the world’s shortest commercial runway is located at Juancho E. Yrausquin Airport on the tiny Caribbean island of Saba. It has a length of 400 meters. Meanwhile, if an airport is to be capable of welcoming larger widebody jets, it needs to provide a runway of at least 2,400 meters at sea level.

Airport runways are usually made of concrete or asphalt. Photo: Dmitrij Rodionov via Wikimedia Commons

Runways also need to be able to withstand significant loads. The world’s busiest airports can, under normal circumstances, have planes landing every 40 seconds. Although they are often referred to as “tarmac,” runways are very seldom actually built from this material. Instead, they are usually constructed from concrete or asphalt.

The runway’s surface is often grooved to make sure that an aircraft’s wheels can gain traction and prevent aquaplaning. The latter occurs if a layer of water was to build up between wheels and the road surface.

Routine maintenance an overnight affair

Runways must be kept in tip-top shape at all times. Routine maintenance can be performed overnight when there are no scheduled landings or departures. This includes the re-painting of markings or numbers, repairing cracks and resealing joints, or cutting surrounding grass. However, occasionally, the airport may need to close the runway entirely, for instance, to renew the top surface.

Gatwick aerial view
Parallel runways will have the same numbers as those at Gatwick Airport but are differentiated by letters. Photo: Getty Images

How are they numbered?

To help pilots navigate safely, airport runway markings and signs are standardized globally. Every runway in the world has two numbers on it. These are between 1 and 36, corresponding to compass directions, and painted on opposite sides of the runway.

The first number shows the magnetic heading of the runways azimuth in decadegreeswhereas the second one is the opposite direction, 180 degrees from the first. They are always rounded to the nearest ten degrees, with the final digit dropped.

Of course, if an airport has parallel runways, this means that the runways will have the same numbers as each other. They will then be designated a letter as well: L, C, or R, signifying Left, Center, or Right.

Meanwhile, as the Earth’s magnetic field is continuously shifting by about 60 km per year, this means that runways often need to be renumbered and renamed.  For example, in 2018, Geneva Airport changed its runway numbers. It replaced close to 100 sign panels and used about 150 kg of paint in the process.

Heathrow runway queue
Runways are numbered according to compass directions. Photo: Getty Images

The importance of navigational accuracy

The FAA usually checks the readings every five years. However, as late as 2019, the north magnetic pole began moving away from Canada towards Siberia much faster than researchers had expected. This was driven by liquid iron moving about in the Earth’s core and caused scientists to change the model one year early.

The runway numbers must be kept up to date. Normally, an experienced pilot should be able to tell if the airport hasn’t replaced them in time. However, when this is not the case, it can have dire consequences.

In 2006, Comair Flight 5191, marketed as a Delta Connection flight, crashed after the pilots failed to pick up on cues that they were on the wrong runway at Blue Grass Airport in Lexington, Kentucky. Instead of using the assigned runway 22, they tried to take off from runway 26, 40 degrees off. Out of the 50 people on board, only one, the flight’s first officer, survived.

Qatar is back to serving 100 destinations this week
Now and then, airports need to change the numbers on their runways as the magnetic poles shift. Photo: Getty Images

Runway incursions

When an aircraft (or other vehicle or person) is on a runway without permission, this is called a runway incursion. These can be of three different categories: operational incidents, pilot deviations, or vehicle/pedestrian deviations.

Operational incidents occur when an air traffic controller’s action results in two or more aircraft ending up too close to one another. This is also the category for an aircraft being cleared to land or take off on a closed runway.

On the other hand, if a pilot fails to comply with an ATC instruction, such as crossing a runway without clearance, this is a pilot deviation. Vehicle and pedestrian deviations are any movements by either one on the airport’s taxiways and runways without having obtained clearance.

All you want to know about runways
If an aircraft is on a runway when it shouldn’t be, this is known as a runway incursion. Photo: Getty Images

O’Hare tops the list with eight

The title of most runways in the world belongs to Chicago’s O’Hare airport, which boasts an entire eight. Second place also belongs to a US airport, namely Dallas-Fort Worth, with seven, while third place goes to Amsterdam’s Schiphol with six.

What else do you think is noteworthy about runways? Let us know your thoughts in the comment section.