How runways are designated
Created | Updated Sep 26, 2002
Did you know that runways have names? Not names like "Bob" or "Polly". Instead, they have numbers for names. And not just any number, only numbers from 1 to 36. Occasionally, some runways have a letter at the end of their name. More about that later.
The numbers are derived by rounding the compass bearing of the runway from one end to the nearest ten degrees, dropping the last digit and putting a zero on the beginning if it would be a single digit. Thus, one number is the reciprocal1 of the other. If a runway is aligned North-South, then it is 18/36, not 00/18. The lowest number is always listed first.
When pilots and air traffic controllers refer to a runway, they only use the number that applies to the end the pilot will be landing on. Thus, if the pilot is landing on Runway 09/27 heading the to east, they are using Runway 09, not Runway 27.
Two examples
If the compass heading of a runway is 122°, you would round it to 120 and drop the last digit, leaving you with 12. Thus, the runway is 12/30.
If the compass heading of a runway is 37°, you would round it to 40 and drop the last digit, leaving you with 4. Since this is a single digit, you put a zero on the beginning, giving you 04. Thus, the runway is 04/22.
Reciprocal runway numbers
| North/East end | South/West end |
| 01 | 19 |
| 02 | 20 |
| 03 | 21 |
| 04 | 22 |
| 05 | 23 |
| 06 | 24 |
| 07 | 25 |
| 08 | 26 |
| 09 | 27 |
| 10 | 28 |
| 11 | 29 |
| 12 | 30 |
| 13 | 31 |
| 14 | 32 |
| 15 | 33 |
| 16 | 34 |
| 17 | 35 |
| 18 | 36 |
So, about those letters...
Some airports have multiple runways that are parallel to each other. Obviously, you can't give such runways identical names or you'll have very confused pilots2. Such runway numbers are followed by "L", "R" or "C"3.
Airports that are in very northern regions, such as northern Canada or Alaska, have a "T" after the runway number. This indicates to pilots that the number is based on the true bearing, rather than a magnetic bearing. True bearings are used because the magnetic north pole is not stationary and thus using a magnetic bearing results in problems. Also, compass readings become unpredictable when you're close to the magnetic north (or south) pole.
1This is a term particular to navigation and compasses. If you prefer, think of it as the complement or modulus of the heading.2A confused pilot is a bad thing.3For Left, Right or Centre, respectively.
