https://aerosavvy.com/aircraft-pressurization/ >Pressurization systems are designed to keep the interior cabin pressure between 12 and 11 psi at cruise altitude. On a typical flight, as the aircraft climbs to 36,000 feet, the interior of the plane “climbs” to between 6000-8000 feet. > Why not keep the cabin at 14.7 psi to simulate sea-level pressure and maximize comfort? The aircraft must be designed to withstand differential pressure, that’s the difference between the air pressure inside and outside the aircraft. Exceeding the differential pressure limit is what makes a balloon pop when it’s over inflated. The greater the differential pressure, the stronger (and heavier) the airplane must be built. It’s possible to build an aircraft that can withstand sea-level pressure during cruise, but it would require a significant increase in strength and weight. A 12 psi cabin is a good trade-off.