They're used by travellers around the world hundreds of thousands of times a day, but where do runways get their numbers from?
It's actually pretty simple.
Let's use Auckland as an example. As with all airports, the runway at New Zealand's busiest has two numbers - one at each end.
If you're flying in from the east, heading west, it appears as though you land on 'runway 23'.
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Clearly Auckland Airport doesn't have 23 runways, so where does the number come from?
The answer can be found by using a compass: From the east, you're flying to a heading of 230 degrees, and abbreviated for efficiency this is shortened to 23.
Likewise, if you're approaching from the west and flying in an easterly direction, you'll be landing on runway 05. That's because you're flying at a heading of 50 degrees.
At larger airports where there are parallel runways, then left and right is used - for example, London's Heathrow Airport has runways 09 left and 09 right.
Now that you've got this covered, you're one step closer to becoming a pilot.
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