Why is flying cheaper than train?

Related questions

1. Can you exchange train tickets?
2. What would Nationalising the railways mean?
3. How long does the TGV take from Paris to Nice?
4. Should the railways be Nationalised?
5. Are French railways Nationalised?
6. Can you buy TGV tickets at the station?
7. How much does it cost to change a train ticket?
8. What is the slowest train?
9. Can I change Advance single ticket?
10. Can I take another train with same ticket?

Tags

1. #cheap
2. #reason
3. #variable
4. #being
5. #trains
6. #train
7. #first
8. #tickets
9. #cheaper
10. #customers
11. #europe
12. #expensive
13. #operators
14. #distance
15. #flights
16. #fares
17. #airline
18. #might
19. #travel
20. #companies