Definition
An idealized atmospheric condition in which the air mass is not moving relative to the ground, so an aircraft's path through the air and its path over the ground are identical. Used as a baseline reference for performance calculations and for teaching the effects of wind on flight.
Plain English
Air that isn't moving. With no wind to push the airplane sideways or change its speed over the ground, the airplane goes exactly where it's pointed.
Context Anchor
Used when learning drift and ground track control, especially to compare what happens with no wind versus what happens when wind moves the airplane off its intended path.
Derivation
Still comes from an old English word meaning quiet or motionless. In aviation, still air means the air itself is treated as motionless over the ground, which makes it a useful starting point before adding wind effects.
Why Pilots Care
Establishes the baseline where heading and ground track are identical, allowing accurate calculation of wind corrections when air is not still.
Grounding Statement
Picture smoke rising straight up from the ground with no sideways movement; that is the kind of no-wind condition meant by still air.
Intuition Check
Still air does not mean the airplane is still. It means the air around the airplane is not moving sideways over the ground.
Example Sentence 1
In still air, the airplane's track over the ground matches its heading exactly.
Example Sentence 2
Ground speed equals true airspeed when flying in still air with no wind component.