Learn the VHF, UHF and HF bands used by air traffic control, including civil voice, military ATC, oceanic coverage and emergency channels.
Air traffic control mainly uses the civil VHF airband from 118.000 to 136.975 MHz, with AM voice and line-of-sight coverage. Military ATC also uses UHF, broadly 225–400 MHz, while oceanic and remote services use selected HF channels, roughly 2.8–22 MHz, for communication beyond VHF range.
In our Aviation & Real-World Flying coverage, an “ATC frequency” normally means a VHF voice channel. Exact assignments, channel spacing and permitted uses vary between countries, so pilots must use the applicable aeronautical charts, publications and controller instructions rather than treating an entire band as available.
Which ATC band is used for each type of flight?
VHF is the normal choice for civil ATC, while UHF serves military aviation and HF covers routes beyond reliable line-of-sight radio range.
| Service | Frequency band | Normal mode | Typical use |
|---|---|---|---|
| Civil ATC voice | 118.000–136.975 MHz VHF | AM | Clearance, ground, tower, approach, departure, centre and flight-information services |
| Military aeronautical and ATC voice | Broadly 225–400 MHz UHF | AM | Military airfields, control agencies and military aircraft; many facilities also provide a paired VHF channel |
| Oceanic and remote voice | Selected HF channels, approximately 2.8–22 MHz | Upper sideband SSB | Long-range communication where VHF coverage is unavailable, sometimes through a ground radio operator |
Not every frequency inside these ranges belongs to ATC. The civil aeronautical communications band also carries weather broadcasts, flight-information services and operational channels. Likewise, much of the military UHF band is used for purposes other than air traffic control.
Why can the same ATC frequency be used in different places?
VHF channels can be reused because their practical coverage is mostly limited by the radio horizon, terrain and transmitter placement.
An aircraft at cruising altitude can contact a VHF station much farther away than an aircraft sitting on the ground. Mountains and buildings may block reception, while remote transmitter and receiver sites let one control centre cover a larger sector. Our explanation of how altitude and terrain determine VHF ATC range covers the distance calculations and limitations.
Frequency planners separate co-channel facilities far enough to reduce interference, but high-altitude pilots can occasionally hear distant controllers or aircraft using the same channel. Hearing another facility does not mean the tuned frequency is wrong if the assigned controller remains readable.
Are 8.33 kHz and 25 kHz separate frequency bands?
No; 8.33 kHz and 25 kHz describe channel spacing within the same civil VHF communications band.
Many regions still use 25 kHz channels, while much of European airspace requires 8.33 kHz-capable equipment, subject to local rules and exemptions. Some six-digit 8.33 kHz radio readouts are channel designators rather than literal carrier-frequency displays, so pilots should enter the number exactly as published or assigned instead of rounding it.
A 25 kHz-only radio cannot select every 8.33 kHz channel. In simulators, support varies: some aircraft model the channelisation correctly, while simpler radio panels may accept only conventional spacing.
Does CPDLC use an ATC radio frequency?
CPDLC does not have one universal voice frequency for pilots to tune.
Controller–pilot data link messages can travel through VHF data link, HF data or satellite systems, depending on the aircraft and operating area. Voice radio remains available for initial contact, urgent instructions and data-link failures. See our overview of voice, HF and data-link communication with controllers for how these systems fit together.
Navigation and surveillance frequencies are also separate from ATC voice. VOR and ILS receivers use the NAV side of the radio installation, while secondary radar and transponders use 1030 and 1090 MHz. ADS-B also uses 1090 MHz and, in the United States, 978 MHz UAT; these are surveillance links, not channels for talking to a controller.
Which emergency ATC frequencies should pilots know?
The principal emergency channels are 121.500 MHz for civil VHF and 243.000 MHz for military UHF.
- 121.500 MHz: the international civil aeronautical emergency frequency, commonly called VHF guard.
- 243.000 MHz: military UHF guard, also used for military distress and interception procedures.
These frequencies are not general-purpose calling channels. If normal communication fails, a pilot would normally try the assigned frequency again, check the radio and audio-panel configuration, try the previous or next appropriate frequency, and use 121.500 MHz when necessary. The often-mentioned 123.450 MHz channel is not an ATC emergency frequency.
How should pilots and simmers tune an ATC frequency?
Tune the exact assigned channel into a COM radio, make it active and ensure the correct receiver and microphone are selected on the audio panel.
- Verify the source: use the controller’s hand-off, a current chart, airport publication or the simulator’s ATC interface.
- Enter the full channel: place it in the COM standby window without rounding an 8.33 kHz assignment.
- Swap it to active: leaving the new frequency in standby is one of the most common causes of apparent radio failure.
- Check the audio panel: select the same COM radio for reception and transmission. COM1 tuned correctly will not help if the microphone remains assigned to COM2.
- Confirm reception: listen before transmitting and read back the hand-off or clearance as required.
ATC voice belongs in COM1 or COM2, not NAV1 or NAV2. The practical distinction is explained in our guide to using COM and NAV radios in a flight simulator. If a simulator still produces silence, check that the active radio has electrical power, the volume and squelch are sensible, and the aircraft’s audio panel is not set to another transmitter.