TIL airport runway numbers are named for the direction in which they point:

- Take the runway number, multiply by 10
- That angle is the direction of the runway

So runway 9 points due east (90°) and runway 27 due west (270°).

The same physical runway will change numbers if they switch the direction of traffic.

#Airport #Airplanes #Math https://en.wikipedia.org/wiki/Runway

area of surface used by aircraft to takeoff from and land on

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