[The_Victor]

Except the plane could not maintain a cabin altitude of less then 10k feet at that altitude, requiring supplemental oxygen.

First off, the human body can tolerate altitude up to ~18 to 20,000 feet without hypoxia being an issue, i.e. no supplimental O2 required. But even that aside, the pressure is controlled by an electronic relief valve that can be set to higher or lower equivalent altitudes by the captain. The only issue becomes the pressure differential that the pressure shell is designed for. 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.

[Atlas Sneezed]

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.

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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).