How are airport codes assigned?

Related questions

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Tags

1. #fields
2. #which
3. #chicago
4. #airport
5. #cities
6. #weather
7. #somehow
8. #transmitters
9. #field
10. #radio
11. #determined
12. #stations
13. #codes
14. #orchard
15. #cases
16. #example
17. #original
18. #located