How does air density change with altitude?

As altitude increases, air density decreases due to the reduction in the mass of air above a given level in the atmosphere. At higher elevations, the pressure of the air decreases because there is less weight of air pressing down from above. This results in particles of air being more spaced out, leading to a lower density. The relationship between altitude and air density is a fundamental concept in atmospheric science and is crucial for understanding principles related to aviation, such as lift generation and aircraft performance.

The options suggesting an increase in density, constancy, or random fluctuations do not accurately reflect the predictable behavior of air as one ascends into the atmosphere. In practice, this decrease in air density with altitude has important implications for aircraft engines, aerodynamics, and weather patterns.