[jlogajan]

I don't see how this guy could've survived four hours at FL300.

That is very strange. Is there another case on record of someone surviving altitudes above 15k feet for hours on end?

[Technocrat]

I'm quite comfortable flying my hang glider at 16k+ for many hours. I start feeling it whenever I get too much above 18, though.

[irishtenor]

Try most of the mountains in Nepal.