# How Runways Are Designated

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 01 to 36. Occasionally, some runways have a letter at the end of their name (more about that later).

A runway designation consists of two numbers each of two digits, one number being the reciprocal of the other. (This use of the term 'reciprocal' applies to navigation and compasses. It means the two numbers differ by 180°. If you prefer, think of it as the complement or modulus of the heading.)

One number is formed by rounding the compass bearing of one end of the runway up or down to the nearest 10° and dropping the last digit; if this results in a single digit, add a zero to the left of it. The other number is the reciprocal of the first number (see the table of Reciprocal Runway Numbers below). If a runway is aligned north-south, then it is 18/36, not 00/18. The lower number is always listed first.

When pilots and air traffic controllers refer to a runway, they use only the number that applies to the end the pilot will be landing on. Thus if the pilot is landing on Runway 09/27 heading to the east, they are using Runway 09, not Runway 27.

### Examples

If the compass heading of a runway is 122° you would round it down to 120 and drop the last digit, leaving you with 12. Thus it is called Runway 12/30.

If the compass heading of a runway is 37°, you would round it up to 40 and drop the last digit, leaving you with 4. Since this is a single digit, you add a zero to the beginning, giving you 04. Thus it is called Runway 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