UNICOM stands for Universal Communications. A UNICOM frequency is a radio frequency used in general aviation which has been assigned to a non-governmental fixed base station. In other words, a UNICOM frequency is generally a useful means of communicating with airport facilities which are not official air traffic control facilities or personnel. On uncontrolled airports (small airports which do not have a control tower), if a Fixed Base Operator (FBO) does business on the airport they will generally have a UNICOM frequency assigned for their use - and in most cases, if they are the only permanent presence at the airport, that UNICOM frequency will also be designated as the airport's Common Traffic Advisory Frequency. Radio calls made on UNICOM/CTAF frequencies are generally prefaced by the intended recipient, as in "Northampton traffic..." to indicate a CTAF transmission or "Northampton UNICOM..." or "Northampton Radio..." for transmissions meant for the UNICOM operator at the Northampton facility.
The UNICOM frequencies are reserved by the Federal Communications Commission in the U.S. for UNICOM use. The frequency used for airports which have a full time control tower or full time FAA flight service station (FSS) is 122.950 MHz. For uncontrolled airports, the following frequencies are reserved:
- 122.700 MHz
- 122.725 MHz
- 122.800 MHz
- 122.975 MHz
- 123.000 MHz
- 123.050 MHz
- 123.075 MHz
From the Code of Federal Regulations of the United States, Title 47 - Telecommunication, Subchapter D - Safety and Special Radio Services, Part 87 - Aviation Services Subpart G Section 87.217
UNICOM is distinguished from MULTICOM in that a UNICOM frequency is assigned to a particular ground station, even though aircraft in the region may use the frequency to communicate directly with each other as in CTAF use. In addition, it should be clearly understood that airports may, and larger airports almost certainly will, have both control tower and UNICOM frequencies. In that case, the control tower frequency should be used for all traffic relating to aircraft operations, and the UNICOM frequencies should be used to communicate with their particular licensees. For example, pilots approaching a controlled airport might call an FBO on UNICOM while several minutes out to request a fuel truck, or to inquire about the availability of rental car service; or they might call a FSS to get weather and facility updates. Neither of these would obviate the need for them to communicate with the control tower using its assigned control frequency.