AIM ¶ 4-1-1 — Air Route Traffic Control Centers
AIM 4-1-1 explains ARTCC (Center) role: providing IFR ATC service in controlled airspace during en route flight. Study guide for pilot students.
Air Route Traffic Control Centers (ARTCCs) — usually called "Centers" on the radio — are the FAA facilities responsible for handling traffic between terminal areas. Per AIM 4-1-1, their primary purpose is to:
- Provide air traffic service to aircraft operating on IFR flight plans
- Work traffic within controlled airspace
- Handle aircraft principally during the en route phase of flight
In practical terms, after you depart and are handed off from Departure Control, you'll typically talk to a Center controller for the cruise portion of your IFR flight, then get handed to Approach Control as you near your destination. Centers cover huge geographic areas (the U.S. is divided into roughly 20 ARTCCs domestically), and each Center is subdivided into sectors — which is why you'll change frequencies multiple times during a long en route segment.
While Centers focus on IFR traffic, VFR pilots can also request VFR flight following (workload permitting) to receive traffic advisories from Center controllers in areas not covered by an Approach facility.