Aviation Radio Frequency Guide

ATIS

Automatic Terminal Information Service

Continuous broadcast of recorded information containing essential operational information for arriving and departing aircraft. Identified by a phonetic letter code (Alpha, Bravo, etc.) that changes with each update.

Larger airports may have separate Arrival ATIS and Departure ATIS frequencies.

TWR

Tower

Controls aircraft operating on the runways and in the vicinity of the airport. Tower controllers issue takeoff and landing clearances and manage the traffic flow in the airport's immediate airspace.

GND

Ground

Controls aircraft and vehicle movements on the airport's taxiways and aprons (but not the active runways). Ground controllers issue taxi instructions and manage the flow of traffic on the ground.

APP

Approach

Controls aircraft approaching an airport, typically within about 30-50 nautical miles. Approach controllers sequence arriving aircraft, issue approach clearances, and provide separation from other traffic.

DEP

Departure

Controls aircraft departing from an airport. Departure controllers ensure separation between departing aircraft and guide them to their en-route airways.

CLD/DEL

Clearance Delivery

Issues IFR (Instrument Flight Rules) clearances and departure instructions to aircraft before they taxi. At busy airports, this service helps reduce frequency congestion on Ground and Tower frequencies.

CTAF

Common Traffic Advisory Frequency

Used at non-towered or part-time towered airports for pilots to coordinate their movements with each other. Pilots announce their positions and intentions on this frequency.

UNICOM

Universal Communications

Non-government air/ground radio communication station that may provide airport information at public use airports where there is no tower or Flight Service Station. Often operated by the airport's Fixed Base Operator (FBO).

FSS

Flight Service Station

Provides information services such as weather briefings, flight plan filing, and can relay ATC clearances. Flight Service Stations also monitor emergency frequencies.

CNTR/CTR

Center

Air Route Traffic Control Center (ARTCC) that controls aircraft in the en-route phase of flight at higher altitudes between terminal areas. Center controllers provide separation between aircraft and route them efficiently.

AWOS/ASOS

Automated Weather Observing System/Automated Surface Observing System

Automated systems that provide continuous weather reports at airports, broadcasting on their dedicated frequencies. They report wind, visibility, cloud coverage, temperature, and more.

RDO

Radio

General designation for radio communications facilities. May include company frequencies or specialized communications stations.