What is preclearance at airport?

Related questions

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4. How many hours before flight can you enter airport?
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6. Why do Canadian airports begin with Y?
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Tags

1. #airport
2. #terminal
3. #customs
4. #inspections
5. #prior
6. #bound
7. #purpose
8. #immigration
9. #dublin
10. #agriculture
11. #facility
12. #uscbp
13. #passengers
14. #departure
15. #undertake
16. #built
17. #preclearance
18. #allows