Airspace means the portion of the atmosphere controlled by a particular country or, more generally, any specific portion of the atmosphere.
Aviators divide airspace into three basic types:
- Uncontrolled Airspace is airspace in which air traffic control does not exert any authority. It exists close to the ground or in mountainous terrain where safe IFR flight and radar coverage are impossible.
- Controlled airspace exists almost every place else. Air traffic control is capable of directing aircraft in this airspace (though does not necessarily do so).
- Special use airspace includes things like areas where flight is prohibited for national security reasons.