Learn how online ATC networks connect flight simulators to human controllers, voice, flight plans and traffic, plus the setup mistakes to avoid.
Online ATC networks connect a flight simulator to shared servers through a pilot client. The client sends the aircraft’s position, transponder and flight-plan data, while human controllers use radar software and voice channels to issue clearances. Other pilots appear through model matching, creating one coordinated multiplayer airspace.
What does an online ATC network actually connect?
An online ATC network links your simulator, pilot client, nearby pilots and human controllers without replacing the simulator’s own flight model or scenery.
Across general-purpose flight simulators, the simulator continues to calculate the aircraft’s movement. A separate client or plug-in reads that movement through the simulator’s interface and sends regular position updates to the network. Our explanation of VATSIM’s network architecture shows how this arrangement works on a widely used volunteer network.
| Component | What it does |
|---|---|
| Flight simulator | Runs the aircraft, cockpit systems, weather and scenery. |
| Pilot client or plug-in | Sends position, altitude, heading, speed and transponder data; receives traffic and voice information. |
| Network servers | Distribute aircraft data, flight plans, controller coverage and communications. |
| Controller software | Displays pilots on a radar-style screen and provides flight strips, coordination and voice facilities. |
| Model matching | Uses locally installed models to depict each connected pilot’s aircraft type and, where available, livery. |
Voice is usually tied to the active COM radio. Tuning a staffed frequency allows the client to connect to that controller’s voice channel; reception range and radio-quality effects depend on the network and client. Controllers issue instructions, but they cannot operate your autopilot or fly the aircraft for you.
Tower, approach and area control may be staffed by different people. The division of responsibility is covered in our guide to ATC positions and their duties.
How does a typical online ATC flight work?
A normal online flight progresses from connecting at a parking stand to filing a flight plan, contacting controllers, receiving hand-offs and disconnecting after arrival.
- Install the approved client: Use the pilot software or plug-in supported by both the network and your simulator. Most networks require desktop software, so console versions of flight simulators normally cannot connect directly.
- Connect while parked: Choose a valid callsign and connect at an unoccupied stand with the transponder in the appropriate ground or standby state. Connecting on a runway or while airborne is a common rule violation.
- File a flight plan: Enter the aircraft type, equipment, departure, destination, cruising level and route. Filing does not normally programme the aircraft’s FMS; the route must also be entered or imported into the cockpit correctly.
- Check controller coverage: Obtain any available ATIS information, tune the published frequency and make the initial call using the aircraft callsign. If nobody is controlling the area, follow that network’s advisory and self-announcement procedures.
- Follow clearances and hand-offs: Read back headings, altitudes, runway clearances and other safety-critical instructions. Retune when transferred to the next controller.
- Finish at the stand: After landing, follow taxi instructions, park clear of movement areas and disconnect when finished.
The exact installation method varies by simulator. For example, our X-Plane 12 online ATC setup walkthrough explains how a simulator plug-in, model matching, flight-plan filing and voice configuration fit together.
How is online ATC different from built-in simulator ATC?
Online ATC uses human controllers and connected pilots, while built-in ATC is generated by the simulator and usually communicates through menus or synthesised voices.
| Feature | Online ATC network | Built-in ATC |
|---|---|---|
| Controller | A real person using controller software | Simulator-controlled software |
| Coverage | Only where controllers are logged in | Available wherever the simulator provides it |
| Communication | Live voice, with text support where permitted | Menus, shortcuts or speech-recognition features |
| Traffic | Other connected pilots | AI or native multiplayer traffic |
| Instructions | Adapted to traffic, workload and pilot requests | Limited to programmed logic and phrase sets |
Built-in ATC is easier when practising privately or learning an unfamiliar aircraft. Human-controlled networks are better when realistic radio work, changing traffic situations and controller coordination matter most. Our guide to using Microsoft Flight Simulator’s built-in ATC provides a practical comparison with the menu-driven approach.
Why is online ATC not working correctly?
Most online ATC failures come from radio configuration, missing model-matching rules, conflicting traffic sources or a misunderstanding about controller coverage.
- No controller answers: A network does not provide automatic replacement ATC when volunteers are offline. Check whether your airport or airspace is actually covered and whether you have tuned the correct frequency.
- You cannot hear voice: Confirm that the intended COM radio is active, the avionics are powered, the correct audio device is selected and push-to-talk is assigned in the pilot client. Also check that the frequency is in the active rather than standby window.
- Aircraft are missing or look wrong: Install a suitable model library, verify its path in the client and use the correct ICAO aircraft code when connecting. The client substitutes another model when it cannot find a match.
- Traffic appears twice: Native multiplayer, live traffic or AI traffic may be displaying the same area alongside network aircraft. Disable conflicting traffic sources according to the pilot client’s instructions.
- The controller expects a different route: The filed network route and the route programmed in the FMS are separate. Compare both before requesting clearance and amend one if they disagree.
- Taxiways do not line up: Pilots and controllers may have different airport scenery. Use an appropriate airport diagram, state that your scenery differs and never cross a runway simply because the painted layout does not match the instruction.
Slew mode, large time acceleration, prolonged pauses and instant repositioning can also produce implausible position updates or break separation. Each network sets its own rules for these functions.
Do controllers cover the whole flight?
No; online ATC coverage depends on which controllers are logged in, and a flight may pass through staffed and unstaffed airspace.
Some networks use top-down coverage, allowing an area controller to provide certain services normally handled by lower positions when those positions are empty. The exact responsibility varies, so check the displayed controller information rather than assuming that a nearby controller covers your airport.
A controller may also log off before the flight ends. Continue under the network’s uncontrolled-airspace procedures, monitor the designated advisory channel and contact the next controller when coverage resumes.
Can beginners use online ATC networks?
Yes, but a beginner should know the chosen aircraft well enough to hold an assigned heading, altitude and speed while operating the radios and transponder.
Start at a quieter airport rather than during a large event. Prepare the route, expected runway and likely frequencies before connecting, and keep a pen or digital scratchpad ready for clearances. If an instruction is unclear or beyond the aircraft’s capability, say “say again” or “unable” rather than guessing.
Read the network’s rules before the first flight. Built-in multiplayer access does not create an online ATC connection, and normal entertainment multiplayer behaviour—spawning on runways, ignoring clearances or performing aerobatics near controlled traffic—can disrupt everyone sharing that airspace.