Since the service ceiling of the 777 is ~42,000ft I would assume they intended the shell to be able to handle a normal cabin pressure at that altitude.
Because the pressure at 42k is about 15% that at sea level, it’s only about 15% more stress on the plane to remain pressurized in a vacuum. Which is nothing compared to safety margins. (Yes, I know that it’s not 1 ATM inside at 24k feet, but the principle still applies).
Because the pressure at 42k is about 15% that at sea level, it’s only about 15% more stress on the plane to remain pressurized in a vacuum. Which is nothing compared to safety margins. (Yes, I know that it’s not 1 ATM inside at 24k feet, but the principle still applies). They're probably using a factor of safety of 1.1 on the pressure shell. That would be typical for the aerospace industry with load conditions well established. But your point is well taken that if the aircraft could maintain lift, the pressure shell will likely hold.