• ARTCC: Air Route Traffic Control Centers.
  • TRACON: Terminal Radar Approach Control Facilities.
    • manage the airspace surrounding busy airports; handle the airspace below 20,000 feet and within 30 to 50 miles of the airport.
    • callsign: approach, departure.
    • only 27 TRACON in the US.
    • e.g. NorCal Approach, serves San Francisco, San Jose, Oakland, Sacramento, Reno plus the other smaller airports with airport traffic control towers.
  • Tower / Ground / Ramp
  • FSS: Flight Service Station.
    • not responsible for giving instructions or clearances or providing separation.
    • callsign: radio.
    • not controlling traffic.
    • e.g. Oakland Radio, Prescott Radio.

Tower vs ARTCC vs TRACON

Towers handle airport operations, ARTCCs/En-route handle cruise phase, and TRACONs handle climbing and descending aircraft, as well as aircraft transiting between ARTCCs in their controlled areas.

Tower and TRACON

TRACON may be on a separate site or colocate with a tower. For example, California has 5 TRACON, 3 of them colocate with a tower (Santa Barbara, Fresno, Bakersfield) and 2 are independent (Northern California TRACON, near Sacramento; Southern California TRACON, near San Diego).

Clearance Frequency

Clearance Delivery Frequency is initial clearance from ATC before you take off.