Originally Posted by CharlesMD
Dude, that was outer space!
P.S. That link from Embry is so fascinating. One question I had though is I didn't quite follow why planes go to a higher altitude as they burn off fuel. Is it because they are lighter and therefore need a lower angle of attack and hence less power? Also, why are turbojet engines more efficient in colder air? I'm sorry physics isn't my stronghold, but airplanes have always fascinated me!
Many aircraft can't climb to their max altitude at their max weight.... so they climb as they burn fuel and their weight goes down.
As for the better performance in colder air... read this article on density altitude. About halfway down it talks about aircraft performance... It explains it better than I can.
http://www.usatoday.com/weather/wdenalt.htm
And here's one from AOPA...
http://www.aopa.org/special/weather/0307jw.html