The United States Federal Aviation Administration (FAA) defines an ARTCC as: [a] facility established to provide air traffic control service to aircraft operating on IFR flight plans within controlled airspace, principally during the en-route phase of flight.
[2] The flight information region controlled by a center may be further administratively subdivided into areas comprising two to nine sectors.
In the United States, centers are electronically linked through the National Airspace System, which allows nationwide coordination of traffic flow to manage congestion.
Pilots may request altitude adjustments or course changes for reasons including avoidance of turbulence or adverse weather conditions.
Controllers can assign routing relative to location fixes derived from latitude and longitude, or from radionavigation beacons such as VORs.
Typically, centers have advance notice of a plane's arrival and intentions from its pre-filed flight plan.
The current list of FIRs and ACCs is maintained by the International Civil Aviation Organization (ICAO).