Why do planes fly at 38000 feet?

Related questions

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2. Can I fly without a transponder?
3. How far can Air Force One fly?
4. What happens if you squawk 7500?
5. Are plane rides scary?
6. Where is a transponder required?
7. Can you fly over Class C airspace without a transponder?
8. Can you flight track Air Force One?
9. How low can a helicopter fly over my house?
10. Can Planes fly over Mount Kailash?

Tags

1. #reach
2. #thinner
3. #flies
4. #speed
5. #plane
6. #burns
7. #altitudes
8. #basically
9. #altitude
10. #require
11. #needed
12. #climb
13. #higher
14. #cruising
15. #which
16. #means
17. #airplane
18. #there
19. #longer