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.
The Great Migration was the movement of some six million African Americans from rural areas of the Southern states of the United States to urban areas in the Northern states between 1916 and 1970.
