CTR

CTR (Control Zone) is a volume of controlled airspace that extends from the surface to a specified upper limit, established around an airport to protect traffic operating in the vicinity. A CTR is typically associated with Class C or D airspace.

CTRs are designed to contain the traffic pattern and instrument approach/departure procedures. Aircraft entering a CTR must comply with the applicable airspace class requirements, including radio communication and, where required, ATC clearance.