[Balding_Eagle]

Hmmm....please note my tagline of Aviator. I have been flying professionally for 35 years. Since you are not familiar with aviation practices and you are not a chemical engineer, you are indeed shooting in the dark.

OK, I make this a direct question, since (in spite of my lack of degrees) I am will to go out on a limb and state that I am positve you are wrong.

My question: Do the fuel tanks on the large airplanes (737 747 etc) operate at whatever elevation pressure the plane happens to be at?

By way of refinement, when the plane is on the runway in LA what is the internal pressure of the tank relative to the outside air pressure? When that same plane climbs to an altitude of 35,000 feet, what is the pressure of the tank, relative to the outside air pressure at 35,000 feet?

[aviator]

Fuel tanks operate continually at ambient air pressure.