What happens to air pressure as altitude increases?

As altitude increases, air pressure decreases due to the thinning of the atmosphere. At higher elevations, there is less air above a given point, which means that the weight of the air pressing down is reduced. This phenomenon occurs because the density of air decreases with altitude; as you ascend, the air molecules become more dispersed. As a result, fewer air molecules are available to exert pressure at higher elevations, leading to a lower overall air pressure compared to sea level.

In aviation, understanding the relationship between altitude and air pressure is crucial for various aspects such as aircraft performance, navigation, and safety, as pilots need to be aware of how these changes can affect lift, fuel consumption, and engine performance.