As your airplane takes off from an airstrip on the ground and rises 30,000 feet into the sky, what happens to the air pressure on the outside of the airplane?

Air pressure, as one of the fluid, depends on the density of fluid, acceleration, gravity, temperature, and depth, respectively height. It does not depend on the mass or volume. When the height increases, the air pressure decreases. At a height of 30000 feet, the air is more diluted, and therefore creates less pressure around the aircraft. The answer is: air pressaure decreases.

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