Which way faster?

Ever wondered why the return flight does not take the same time as the original flight?

Is flying from west to east:
1) slower than flying from east to west.
2) faster than flying from east to west.
3) same as flying from east to west.

Answer is 2, due to the jet stream.

This problem came to me while deciding which way I should fly to US, so I have decided to fly in the westernly direction, its cheaper too. I will be going to UIUC, leaving on 31st July...