ppragman
FLIPY FLAPS!
Jesus, I didn't know they could get that high. F/A-18E/F says 50k plus, so I guess its possible.
Wouldn't wanna fall from that height.
Seriously, if you ever look at the "time to die charts," and "time of useful consciousness charts" I think anything above about FL400 should be considered space. At FL600, you're not that far from the the armstrong limit, that practically is space.
http://en.wikipedia.org/wiki/Armstrong_Limit