Lois Larson
Airport runway numbers are based on magnetic headings, helping pilots align with the correct runway. They are always given as individual numbers combined together, with no whole tens or hundreds used. For example, a runway pointing to 092° is rounded to 090°, resulting in a runway number of 09. The final 'zero' is removed to give a two-digit identifier. If there are multiple parallel runways, they will be labelled with L for left, R for right, and C for centre. For example, runway 15L, 15C, and 15R. A runway numbered 09 points east (90°), runway 18 is south (180°), runway 27 points west (270°) and runway 36 points north (360°).
| Characteristics | Values |
|---|---|
| Number of digits in runway numbers | Runway numbers are always two digits long. |
| Leading zeros | In the US, the leading zero is omitted. In Europe, the leading zero is pronounced. |
| Runway number calculation | The runway number is the nearest 10 degrees to the runway's magnetic heading. |
| North-facing runways | Runways facing true north are designated "36". |
| Parallel runways | Parallel runways are identified by appending left (L), center (C), or right (R) to the end of the runway number. |
| Non-hard surfaces | Runways with non-hard surfaces may use the standard numerical scheme or traditional compass point naming. |
| Special-use runways | Airports that have seaplane waterways may denote the waterway with a "W" suffix. |
| True north vs. magnetic north | Runways numbered relative to true north rather than magnetic north will use the suffix "T". |
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What You'll Learn
Runway numbers are based on magnetic headings
The use of magnetic headings also makes it easier for pilots to identify the runway and land, as the aircraft's heading will align with the runway's heading. For instance, if an aircraft is directed to land on runway 09, the aircraft's heading will be approximately 090° during landing. This convention has been in use for a long time, even before the availability of GPS technology.
Some airports, however, may use true north headings for runway numbers due to high magnetic variation. This is more common in places like northern Canada and Greenland, where magnetic variation can change rapidly due to their proximity to the magnetic north pole. In these cases, switching to true headings avoids the constant need to renumber the runways.
Runways with multiple parallel strips also have additional identifiers, such as "L" for left, "C" for center, and "R" for right. For example, an airport with three parallel runways might have them labelled 26L, 26C, and 26R. This naming convention helps to differentiate between runways pointing in the same direction.
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How to identify left, right, and centre runways
Runway numbers are determined by the approach direction of the runway. The number is the whole number nearest one-tenth the magnetic azimuth of the runway's centre line, measured in a clockwise direction from magnetic north. The letters L, R, or C are used to differentiate between left, right, and centre parallel runways. For example, runway "9L" is pronounced "nine-left".
Runways with multiple parallel runways will be labelled with an additional identifier, such as L for left or R for right. For instance, a runway with the heading 237° will generally be labelled as runway 24. If there are two parallel runways, they will be labelled 24L and 24R for left and right, respectively. If there is a third parallel runway, it will be labelled 24C for centre.
The runway heading is rounded to the nearest 10 degrees, and the zero is removed. This number is then assigned to the runway. For example, a runway with a magnetic heading of 090° will be assigned the number 09. The final 'zero' is removed to give a two-digit identifier.
It is important to note that runway numbers can change over time. This is because the magnetic north pole moves, causing the magnetic azimuth of the runway to change. If the change is significant enough, the runway number will be updated to correspond to the nearest 10°.
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Why runway numbers change
Runway numbers are based on the runway's orientation relative to magnetic north. For example, a runway with a magnetic heading of 135° to 144° will be numbered 14, and one with a magnetic heading of 145° to 154° will be numbered 15. Runway numbers are occasionally changed due to changes in the Earth's magnetic field. The magnetic North Pole can move by as much as 40 miles a year, and this variability can be a problem for pilots and airports. As a result, runway numbers and names need to be changed when the magnetic heading changes by more than 3 degrees.
The FAA orders airports to change runway names once they've changed so much that they'll no longer round to the same number. For example, a runway called 36 wouldn't need to change if the degrees off north went from 355 to 359. But if it went down to 354, it would need to be rounded down to 35, and the name would be changed. This is because runway numbers are determined by rounding the compass bearing of one runway end to the nearest 10 degrees and truncating the last digit, meaning runways are numbered from 1 to 36. The opposite end of the runway always differs by 180 degrees, so it’s numbered 18 higher or lower. For example, Runway 9-27 is oriented east-west.
In addition, at airports with more than three parallel runways, the next series of runways will have their final digit changed by 1 to avoid any confusion, even if the 'extra' runway points in the same direction. For example, if there were four runways, all pointing to 280°, the runway numbers might be designated as 28, 29, 28, and 29. This is because the reciprocal of any runway number varies by 180° as it is the opposite-facing runway. However, since we remove the third and final digit when discussing runway numbers, 180° becomes 18.
Finally, in some cases, runways are referenced to true north headings instead of magnetic north to avoid constantly renumbering them. This is more common in places where magnetic variation is extreme or unstable, such as in parts of northern Canada and Greenland.
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How to read runway numbers when speaking
Runway numbers are based on magnetic headings, which help pilots align with the correct runway. They are always given as individual numbers combined together. For example, runway "22" is pronounced "two-two" and not "twenty-two". This is to ensure clarity and safety.
The numbers are taken from the magnetic heading of the runway, rounded to the nearest 10 degrees, and then the final zero is removed. For instance, a runway pointing to 092° is rounded to 090°, resulting in a runway number of "09". A runway numbered 09 points east (90°), runway 18 is south (180°), runway 27 points west (270°) and runway 36 points north (360°).
If there are multiple parallel runways, they will be labelled with L for left, R for right, and C for centre. For example, runway 15L, 15C, and 15R. If a runway is used in the opposite direction, the number changes accordingly—runway 03L becomes 21R.
Suffixes may also be used to denote special-use runways. Airports with seaplane waterways may use the suffix W, while small airports that host various forms of air traffic may use additional suffixes to denote special runway types, such as S for STOL aircraft, G for gliders, H for rotorcraft, and U for ultralights.
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How to read taxiway signs
Taxiways are designated alphabetically, with single letters of the alphabet for each taxiway, e.g. 'A' for taxiway Alpha, 'B' for Bravo, etc. The letters 'O', 'I' and 'X' are not used. At large airports with many taxiways, double-letter designators may be used, e.g. 'AA', 'BB', etc. or alphanumeric identifiers, e.g. 'A2', 'A3', etc.
Taxiway signs are either mandatory or information signs. Mandatory signs have white characters on a red background and require specific ATC clearance to a point beyond them before they are passed. Information signs have a combination of yellow and black markings and are provided at the discretion of the airport operator to give additional guidance to taxiing aircraft. They include location signs, which are used to identify taxiways and runways at complex intersections.
Taxiway signs are usually black with yellow letters or yellow with black letters and arrows. They can be seen from your airplane window when taxiing to take off. They are designed primarily for pilots but can be understood by passengers who follow along with an airport diagram.
Inbound destination signs guide the route from taxiways to major airport locations. Outbound destination signs will list the runway number and have an arrow pointing in the direction of travel. If the taxiing route for multiple runways is in the same direction, the sign will list each runway number, separated by a black dot. If the routes are in different directions, they will be separated by a vertical black divider line.
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Frequently asked questions
Runway numbers are based on magnetic headings and help pilots align with the correct runway. The numbers are taken from the magnetic heading of the runway, rounded to the nearest 10 degrees, and the final zero is removed. For example, a runway pointing to 092° is rounded to 090°, resulting in a runway number of "09".
Runway numbers change because the Earth's magnetic field shifts and their headings shift with it. This is more common at higher latitudes. For example, Fairbanks International Airport in Alaska renames runways roughly every 24 years.
Airports with more than one runway pointing in the same direction (parallel runways) use the letters L (left), C (centre), and R (right) to identify the position of each runway when facing its direction.
