What effect does an increase in altitude have on air density?

As altitude increases, the density of the air decreases due to the decreasing atmospheric pressure. This phenomenon occurs because, as you rise in elevation, there is less air above you exerting pressure, which results in fewer air molecules in a given volume. Consequently, the air becomes less dense, meaning that there are fewer molecules present per unit volume. This decrease in air density at higher altitudes impacts various aspects of aviation, such as engine performance, lift generation for aircraft, and the effectiveness of control surfaces. Understanding the relationship between altitude and air density is crucial for pilots and aviation professionals, as it influences flight operations and performance calculations.