Pressure changes inside a pressurized aircraft. You may be flying at 30,000 feet, but the internal cabin pressure is that of about 7,000 feet altitude. You can feel the pressure gradually decrease from take off, at ground altitude, until you get to cruising altitude. It's why your ears pop. A scuba diver feels the same ear-popping as he/she descends, or ascends through the column of water.
When the plane begins its descent, the cabin pressure is increased gradually so that the inside pressure is the same as the outside pressure when the plane lands.
So yes, the pressure inside the cabin decreases as the plane climbs, to a level that maintains enough density to insure sufficient oxygen content for human survival, and still nto blow up the plane with too much pressure.
Water will boil at a lower temperature when the plane is at cruising altitude.
Even at the altitude of the Great Lakes, we need to add 11.2 pounds of pressure to get water to boil at the same temperature as it does at sea level. And our altitude is at 702 feet above sea level, not near the 7,000 foot pressure that is in the airplane cabin.
Just sos ya knows.
Seeeeeeya; Chief Longwind of the North
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