Each of the nine regions contains a varied number of FIRs. According to ICAO, the geographical boundaries of the current ICAO air navigation regions are defined in Appendix I to the Directives to Regional Air Navigation Meetings and Rules of Procedure for their Conduct (Doc 8144).

Global airspace is currently divided into approximately 263 Flight Information Regions (FIRs). These FIRs are managed by the International Civil Aviation Organization (ICAO) and are assigned to specific countries to provide air traffic control and alerting services. While the world is divided into nine larger "ICAO Air Navigation Regions" (such as the North Atlantic, European, and Pacific regions), the individual FIRs are the operational "blocks" that ensure safe separation of aircraft. Some small countries manage only one FIR, while massive nations like the United States, Russia, and Canada manage dozens. FIR boundaries often extend far into international waters; for example, the New York Oceanic FIR covers a vast portion of the Atlantic Ocean. These regions are essential for global flight planning, as airlines must pay "overflight fees" to the authority responsible for each FIR they traverse during a long-haul journey.