grid777
What is up with all the caustic hostility here?
Sounds like your sim is generating a genine warning. In real life with most commercial aircraft they are designed to operate at a max differential pressure of less than 9 psi creating a cabin altitude of about 8k feet above sea level. The cabin altuide alert I know of in most aircraft goes off at a cabin altitude of 10.5K feet.
Basically you are operating your simulated aircraft above the specified altitude to provide a safe berathing environment for your sim pax.