Do you go through customs before or after your flight?

Related questions

1. Do you have to pay to drop off at Heathrow?
2. How long before your flight should you check in?
3. Why do you have to be at the airport 3 hours early for international flights?
4. How many planes take off every minute at Heathrow?
5. When should I print my boarding pass?
6. How far is LA from London by plane?
7. Do I have to go through security again for connecting flight?
8. Should I check in online or at the airport?
9. Is there a pick up point at Heathrow Terminal 5?
10. How long does it take to get through arrivals at Heathrow?

Tags

1. #airports
2. #which
3. #immigration
4. #preclearance
5. #general
6. #united
7. #plane
8. #boarding
9. #states
10. #known
11. #after
12. #through
13. #destination
14. #international
15. #before
16. #returning
17. #arrive
18. #customs