Learn

How runways are numbered

Every runway has a number at each end. Once you know the rule, a runway diagram tells you which way the runways point at a glance.

The number is a compass heading

Take the runway’s magnetic compass heading, round it to the nearest 10 degrees and drop the last digit. A runway pointing at 087° becomes runway 09; one pointing at 272° becomes 27.

The two ends of a runway point in opposite directions, 180 degrees apart, so their numbers always differ by 18: 09/27, 18/36, 04/22. Pilots use the number for the direction they take off or land in.

L, C and R for parallel runways

When an airport has parallel runways, letters tell them apart: L for left, C for centre and R for right, as seen by a pilot approaching from that end. That’s why the left runway at one end is the right runway at the other: Amsterdam Schiphol has 04/22, 06/24, 09/27, 18C/36C, 18L/36R, 18R/36L.

Busy airports sometimes run out of letters. Dallas/Fort Worth has 7 runways, so some parallel runways that point the same way are numbered 17 and others 18: 13L/31R, 13R/31L, 17C/35C, 17L/35R, 17R/35L, 18L/36R, 18R/36L.

Why numbers change

Magnetic north slowly drifts, so a runway’s magnetic heading changes over the years. When it drifts far enough, the airport repaints the numbers. In the United States you’ll often see single digits written without the leading zero, such as 9 instead of 09.

Amsterdam Schiphol, drawn to scale with north at the top. Runway 36 points north, 27 west.