airspace

Airspace is the portion of the atmosphere within which air traffic control and aviation regulations apply to ensure safe and efficient flight. It is defined by geographic boundaries and vertical limits and governs the routing, separation, and use of air routes, airways, and procedures. The management of airspace is coordinated internationally by the International Civil Aviation Organization (ICAO) and implemented nationally by aviation authorities such as the FAA, EASA, or corresponding agencies.

Airspace is typically divided into controlled and uncontrolled categories. Controlled airspace requires ATC clearance and provides separation services for instrument flight rules (IFR) traffic; VFR traffic may also be subject to restrictions depending on the class and location. Uncontrolled airspace allows operations without ATC clearance, though pilots must observe minimum weather requirements and self-separation.

Many countries organize controlled airspace into classes or segments. A common framework uses Class A through G, though exact definitions vary. Class A is high-altitude IFR-only airspace; Classes B, C, and D generally surround airports and provide increasing ATC services; Class E is controlled airspace with IFR separation but often not requiring clearance for VFR; Class G is uncontrolled. In addition to these, special use airspace like restricted, prohibited, danger areas, and military operation areas may exist, along with temporary flight restrictions.

Airspace design considers terrain, weather, and traffic demand, and is continuously updated through notices and procedures. The system enables routing, efficiency, and safety in civil and military aviation and supports both fixed-wing and rotorcraft operations worldwide.