ATIS vs UNICOM explained: learn what each frequency provides, when to call and why UNICOM cannot issue air traffic control clearances.
ATIS provides one-way, repeatedly broadcast airport information such as weather, active runways and approaches. UNICOM is normally a two-way air-to-ground frequency used for airport advisories or services, especially at non-towered aerodromes. UNICOM operators do not issue air traffic control clearances or provide aircraft separation.
In Aviation & Real-World Flying, the practical distinction is reception versus conversation: pilots receive ATIS before contacting the relevant control position, while they call UNICOM when they need an airport advisory or ground service. An airport can provide both.
ATIS vs UNICOM at a glance
| Feature | ATIS | UNICOM |
|---|---|---|
| Communication | One-way voice broadcast or digital message | Normally two-way radio |
| Main purpose | Standard airport, runway and weather information | Local airport advisories and ground services |
| Typical use | Before calling clearance delivery, ground, approach or tower | Common at non-towered airports; also used for services at some towered airports |
| Authority | Conveys operational information but is not a control clearance | Provides advice only, not ATC instructions or separation |
| Expected response | No response; pilots report the ATIS identifier to ATC | A ground station may reply, but the frequency may be unattended |
What information does each service provide?
ATIS information
ATIS reduces repetitive controller transmissions by continuously presenting the same essential information to arriving and departing aircraft. A broadcast commonly includes observation time, wind, visibility, cloud, temperature, altimeter setting, runways and approaches in use, plus selected operational remarks.
Each issue receives a phonetic identifier such as Alpha or Bravo. Pilots normally tell ATC they have that information, although a controller must still pass later changes. Our detailed explanation of what an ATIS broadcast contains and how pilots use its identifier covers that process.
ATIS does not replace a complete weather and operational briefing. It contains terminal information selected for immediate airport operations, not every relevant weather report or notice.
UNICOM information
A staffed UNICOM station may provide the reported wind, runway condition, known traffic, suggested runway, parking instructions, fuel availability or other airport services. The exact service depends on the airport and country; some frequencies are monitored by an airport office or fixed-base operator, while others receive no reply.
A UNICOM operator is not an air traffic controller unless that person is separately acting in an authorised ATC role on an assigned control frequency. A runway suggestion is therefore an advisory, not a landing clearance. For the authority controllers actually have, see our guide to ATC roles, clearances and non-towered operations.
Is UNICOM the same as CTAF?
UNICOM and CTAF are related but not interchangeable. UNICOM describes an air-to-ground station or service; CTAF is the designated Common Traffic Advisory Frequency pilots use for traffic calls at an airport without an operating tower.
A UNICOM frequency is often designated as the CTAF, which causes the confusion. However, a CTAF may instead be another published frequency, including a tower frequency used after the tower closes. Pilots should use the published airport data rather than assuming every UNICOM frequency is the traffic frequency.
Can an airport have both ATIS and UNICOM?
Yes. At a towered airport, a pilot might receive ATIS, contact ATC for taxi or landing instructions, and then call UNICOM for parking or fuel. The services have different purposes and neither replaces the other.
At many non-towered airports there is no ATIS. Pilots may obtain automated weather from another listed service, monitor the CTAF and contact UNICOM if a staffed advisory station is available.
How should pilots and simmers use ATIS and UNICOM?
- Check the published frequencies. Confirm whether the aerodrome lists ATIS, UNICOM, CTAF or separate weather and service frequencies.
- Receive ATIS before calling ATC. Note the identifier, runway, approach, weather and any operational remarks. Give the identifier on initial contact when appropriate.
- Use the correct two-way frequency. Contact ATC at a controlled airport. At a non-towered airport, monitor the CTAF before transmitting position and intentions; call UNICOM when an airport advisory or service is needed.
- Treat UNICOM replies as advisory. The pilot remains responsible for runway selection, traffic avoidance and the safety of the operation.
If nobody answers UNICOM, do not assume the airport is closed or the circuit is empty. Continue monitoring the published CTAF, make normal traffic calls and use the published weather source and procedures. A mistake we see in simulators is requesting landing clearance from UNICOM; no such clearance should be expected.
Flight simulators sometimes combine UNICOM and CTAF under one menu or simplify unattended frequencies. For realistic operation, follow the frequency's real function: listen to ATIS, communicate with ATC where control service exists, and use CTAF or UNICOM procedures without treating advisory information as a clearance.