airspace is a portion of the atmosphere controlled by a country above its territory and territorial waters, which is under the country's sovereignty and regulatory control.
Internationally, allocation and management of airspace is coordinated by the International Civil Aviation Organization (ICAO), which was established through the Chicago Convention in 1947 to unify air traffic. ICAO organizes airspace into Flight Information Regions (FIRs) and provides classification guidelines.
National authorities, such as the FAA, CAA, or EASA implement rules and regulations for air traffic control, special-use airspace, and enforcement within their own FIRs.