How Do Airport Runway Numbers Work?

Below is a fantastic picture of one of the three runways of the Brussels Airport:

Brussels Airport Runway 25 R
Brussels Airport Runway 25 R
Credits: Lucash

If you look closely at the runway, you will notice ‘25R’ written on it. Incidentally, it is known as Runway 25R. I don’t need to be a psychic to guess the question which brings you here – how are runways numbered? What makes these numbers unique?

Read on to find out!


Short Answer

Runways are numbered on the basis of the angle the runway makes in reference to the magnetic north pole, also known as the magnetic heading.

Long Answer

As we all know, Earth has a magnetic field around it. Similar to a magnet, Earth’s magnetic field too has magnetic poles (see below).

Magnetic Poles of the Earth
Magnetic Poles of the Earth
Credits: User-Sch

Now imagine a line drawn from the magnetic north pole to the centre of an airport runway. This line will make an opening angle with the runway, considering it as a line segment. This angle is known as the magnetic heading of the runway. Runway numbers are nothing but magnetic heading divided by 10 and rounded off to the nearest integer.

Example time!

In the picture below, the red strip is a runway. If we draw a straight line from the magnetic north (the yellow line in this picture), it will make an angle with the runway, ‘Angle x’ in this case. Thus, the number you will see on the Runway End A will be x divided by 10 and rounded off to the nearest integer. If ‘Angle x’ is 70 degrees, Runway End A would be marked 07.

Runway Numbering
Runway Orientation with Respect to the Magnetic North decides its numbering
Original Image Credits: NASA

What about Runway End B? Though it is the other end of the same runway, it is considered a different one for all purposes. The magnetic heading of this end of the runway will be x + 180 degrees. If ‘Angle x’ is 70 degrees, as in our example, End B should be marked 25 (Can you deduce why?).

Taking the example forward, can you use the compass below to find which direction runway 07 will be pointing towards? What about runway 25?

Magnetic Compass
Use this to find Runway headings!
Credits: Public Domain

Find out the answer here. And don’t forget to like the Facebook page!

What about the R in 25R?

R simply refers to Right!

Airports, at times, have parallel runways. Suffixes L, C and R – standing for Left, Centre and Right – is a terminology used to differentiate them.

If there are more than 3 parallel runways (in rare cases; Los Angeles International Airport, or LAX, is a great example), airports give a slightly different number to some runways. For example LAX has four parallel runways which they name as 24L, 24R, 25L and 25R.

Check out this awesome LAX Airport Diagram! I am sure it will be a great learning.

This was it for today! If you liked the article, don’t forget to share this with fellow aviation enthusiasts. And like our Facebook page for great aviation pictures, videos and articles!

Cover Credits: By UR-SDV – Spotters, Commons

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