Why are flight paths curved?

Related questions

1. Is the Concorde still flying?
2. How do airplanes communicate over the ocean?
3. Why do planes fly over Greenland when crossing the Atlantic?
4. Do any flights go over Antarctica?
5. Why do planes not fly directly over the Pacific Ocean?
6. What determines flight paths?
7. Why do we not feel earth spinning?
8. Can I fly over Antarctica?
9. Why don't planes fly over the Atlantic?
10. Do planes fly over Tibet?

Tags

1. #distance
2. #interestingly
3. #between
4. #rather
5. #because
6. #circle
7. #heading
8. #straight
9. #pilot
10. #slightly
11. #sphere
12. #great
13. #continuously
14. #points
15. #alter
16. #actually
17. #constant
18. #course
19. #shortest
20. #earth