Why does Vy decrease with altitude?

Related questions

1. What is Vy?
2. Why does thrust decrease with speed?
3. How much does it cost to check a bag on Vueling?
4. What is the difference between power and thrust?
5. Does drag increase with altitude?
6. Can I collect BA Avios on Vueling?
7. Does indicated airspeed change with altitude?
8. Does Vueling basic fare include luggage?
9. What is thrust power?
10. What does VY mean in physics?

Tags

1. #increases
2. #fewer
3. #airspeed
4. #pressure
5. #flowing
6. #induced
7. #given
8. #differential
9. #climb
10. #means
11. #attack
12. #decreases
13. #there
14. #molecules
15. #angle
16. #density