"Ralph Nesbitt" wrote in message gy.com...


At altitude A/C cabins are like a pressure vessel. A/C cabins are
pressurized to maintain ~ 12 PSI Gauge, ~ the same as normal atmospheric
pressure @ 11,000' ASL, in the cabin irrespective of altitude above 11,000'

Actually, 8,000' (at least in US certificated transports).