Entering Tibet by plane or train?

[juls2]

It's been forever since I last posted...but I'm on the road again and need some help and I know you guys can do it...

I'm planning a 2-3 week trip to China mid-May of 2010 and have a couple of questions. I am traveling with a friend who has asthma and who really wants to go to Tibet. We are flying in to Beijing first and then traveling to Tibet from there. She's read that going by train is the best method to acclimatize the body. I would prefer the plane only because it would save us time. Of course, I don't want my friend's health to be at risk, so I just need some advice from those who have entered via plane and/or both regarding what the case is really. Also, what are some reliable tour agencies that can help us book our trip to Tibet--I know that's the only way to get in legally at this point.

thanks a million...and I just want to say thanks to this website and the people that are so generous with their advice because you all have helped me achieve my dreams and given me the courage to acknowledge and do what has always been in my soul. Thanks!