I'm running off of memory, so please correct me, I may be wrong about stuff.
Sea level air pressure is about 101 kPa or 14.6 psi, outer space is presumed zero pressure, so techincally, if a volume was design to withstand 14.6 psi, it could go into space...
So why are aircraft like 777 have their fuselage pressurized to 12 psi**? If there was a 50% factor of safety, then 8psi would be an operational max. If they wanted to maintain sea level pressure, they could fly at an altitude that was (14.6 - 8 =) 6.6 psi, FL215. If there was no factor of safety, then FL395 feet.
Do I have that correct?
For example: If I had a plane where the max operating pressure in the cabin (not ultimate) is 10 psi, and the plane were pressurized to 5000 feet, what altitude could it go to regardless of what the wings could do?
** my source was the old "21st Century Jet" special on PBS from 1994. During the pressurization test they went to 12 psi and a leak occured in the rear left exit door, they fixed it.
[Edited 2006-03-08 03:26:35]