FIR

FIR (Flight Information Region) is an airspace of defined dimensions within which flight information service (FIS) and alerting service are provided. Every piece of airspace around the world belongs to a FIR — there are no gaps in coverage.

FIRs are designated by ICAO and managed by the responsible state's civil aviation authority. Key aspects include:

• FIRs extend from the surface upward; above a specified altitude, the upper airspace is designated as a UIR (Upper Information Region)
• Each FIR is identified by a four-letter ICAO designator (e.g., SBCW for Curitiba FIR, EGTT for London FIR)
• FIRs may contain various classes of controlled and uncontrolled airspace
• Air traffic services within a FIR are provided by an Area Control Center (ACC) or Flight Information Center (FIC)

When aircraft cross from one FIR to another, they typically transfer to the frequency of the next FIR's controlling authority. FIR boundaries are defined along geographic coordinates and often follow national borders, though oceanic FIRs can extend far beyond a country's territory.