You know, I thought about it a bit...and I think the OP may have been a bit misled (or not brought entirely up to speed) by the Palm One kid.

I suspect that in actuality said kid was talking about the new MyFi from XM...which is indeed a portable (battery powered...key for use on a plane) radio. But the important item is that is also has an internal hard drive that records/stores like 5 hours of programming...so essestially it's like an iPod (or any other HD-based MP3 player).

I think you'd face 2 issues trying to use a standard XM radio on the plane...powering it could be difficult and placing the antenna (unless you had a window seat) would not be easy.

Just my $0.02