Saw an article today about an aircraft that would change it's buoyancy, so
it would float up like a balloon and then change buoyancy and glide down.
Interesting stuff, although I doubt we'll see it anytime soon. Is something
like this even practical? The article says they take the aircraft up 10
miles to get 400 miles range, I would think ATC wouldn't like the idea of a
free balloon (which is what it would be at that point) up in the flight
levels.

http://www.machinedesign.com/ASP/vie...PACE&catId=379

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Louis Perley III
N46000 - KBJC