April 27, 2026
How Airport Runways Are Named: The Heading System Explained
Runway numbers come from their magnetic heading, rounded to the nearest ten degrees. Runway 27 points west. Runway 09 points east. Here is the full system and how parallel runways are named.
Airport runways are not named at random. Every runway number directly encodes its magnetic compass heading — a system that gives pilots instant orientation information just from the runway designation.
The basic rule
Runway numbers are derived from the runway's magnetic heading, rounded to the nearest ten degrees, then divided by ten. A runway pointing due east (090°) is Runway 09. A runway pointing due west (270°) is Runway 27. The same physical runway has two numbers — one for each direction — and they always differ by 18 (180° / 10).
Runway pairs
Examples of runway pairs at major airports:
- LAX has four parallel runways: 06L/24R, 06R/24L, 07L/25R, 07R/25L
- LHR has two parallel runways: 09L/27R and 09R/27L
- ORD has seven runways in multiple configurations
L, R, and C designators
When two runways share the same heading (parallel runways), they are distinguished by adding L (Left), R (Right), or C (Center) to the number. Chicago O'Hare has so many parallel runways that it uses 10L, 10C, and 10R for its three east-facing runways.
Why magnetic, not true north?
Runway headings use magnetic north because aircraft compasses reference magnetic north, not true north. As the Earth's magnetic field shifts over time, runway designations must occasionally be updated. In 2012, Portland International (PDX) renumbered its main runway from 28 to 29 after magnetic north drift changed its effective heading.