Definition
Air that is holding the maximum amount of water vapor it can contain at its current temperature and pressure. At this point, relative humidity is 100 percent, and any additional cooling or added moisture causes water vapor to condense into visible water droplets such as cloud, fog, or dew.
Plain English
Air that is completely full of water vapor and cannot hold any more at its current temperature. If it cools any further, the extra moisture has to come out as droplets.
Context Anchor
Seen in weather and aircraft performance discussions, especially when learning how humidity affects air density, engine power, and lift.
Derivation
From the Latin saturare, meaning 'to fill' or 'to soak.' Saturated air is air that has been 'filled up' with as much water vapor as it can hold.
Why Pilots Care
Saturated air is less dense than dry air at the same temperature and pressure, which reduces engine power, propeller efficiency, and wing lift.
Grounding Statement
On a warm, muggy day, air near saturation can start forming visible moisture such as fog or cloud if it cools enough.
Intuition Check
Saturated air does not mean the air is full of liquid water. It means the air has the maximum amount of invisible water vapor it can hold under the current conditions.
Example Sentence 1
On a hot, humid afternoon the air near the runway was nearly saturated, and the pilot expected reduced takeoff performance.
Example Sentence 2
The density altitude calculation must account for saturated air because the extra water vapor further lowers air density.