Airport Runways—What Do Those Big Numbers Mean?

Have you ever been looking out the window of a commercial airliner as it approaches an airport, and noticed the big numbers painted at either end of the runways? Those numbers are not random, and play an important part in airport operations.

Airport runway numbers are based on 360-degree compass headings. Runways are typically oriented based on prevailing winds—aircraft take off and landing depends on wind direction. If a runway faces east/west as an example, the compass headings for that runway will be 90 degrees facing east, and 270 degrees to the west. For runway markings, the last digit is dropped after the runway heading is adjusted to the nearest 10 degrees. So, the runway facing east is now Runway 9, and facing west is Runway 27.

Parallel runways facing the same direction are labeled L and R, but a single runway has no need for a L or R designation. Many larger airports use parallel runways to help with traffic flow. Aircraft can take off and land on adjacent runways without interfering with each other. The same runway mentioned above, if joined by a parallel runway facing east, would be labeled 9L and 9R. These runway markings help pilots during takeoffs and landings. For example, a pilot taking off can confirm he or she is on the correct runway, and when landing, can confirm correct alignment.

If you are visiting PIE and are interested in seeing maps that show various aspects of the terminal, runways, or our air carrier routes, visit Choose St. Pete–Clearwater International Airport (PIE) for convenient air travel to/from the greater Tampa Bay region.

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