What happens to air density as air cools?

As air cools, its density increases and it becomes heavier. This phenomenon occurs because cooler air has molecules that are packed closer together than in warmer air. As the temperature drops, the kinetic energy of the air molecules decreases, leading to a reduction in the volume they occupy. This relationship between temperature and density is also described by the ideal gas law, which states that, at constant pressure, a decrease in temperature leads to an increase in density.

In practical aviation contexts, understanding the effect of air temperature on density is crucial for performance calculations. Denser air provides more lift for aircraft, which influences takeoff and landing distances, climb rates, and engine performance. Recognizing this behavior is essential for safe and efficient flight operations.