A free, open-source, voice-first ATC companion for Microsoft Flight Simulator.
Project website · Latest release · Contribute
Want to fly it? Download the Windows installer or portable ZIP.
Want to improve it? Pick a good first issue
or read the contributor quickstart.
StormATC is an entertainment product for flight simulation only. It must not be used for real-world aviation, navigation, flight planning, or air traffic control.
StormATC gives a simulated flight a controller to talk to. You press a key, say what a pilot would say, and a controller answers — with clearances that follow procedure, readbacks that are actually checked, and handoffs that happen when they should.
It is deliberately modular and bring-your-own-API-key. The application is free; the optional speech and language services are third-party products you connect with your own accounts.
It is not a real-world tool, and it is not a replacement for anything used in real aviation. It is not affiliated with, derived from, or compatible with any commercial ATC add-on. All code, prompts, data, and interface in this repository are original.
Everything in StormATC follows from one rule:
The simulator determines what is physically true. The deterministic ATC engine determines what is permitted. The language model helps understand the pilot and express approved instructions naturally.
A language model is never authoritative for aircraft position, altitude, heading, speed,
configuration, frequency, runway availability, traffic separation, squawk codes, taxi routes,
cleared altitudes or routes, assigned headings, controller jurisdiction, flight phase, whether a
readback was correct, or whether a takeoff or landing clearance is available. Those come from the
simulator and from StormAtcStateEngine, which is ordinary, testable, deterministic C#.
Where a model is used, its output is treated as untrusted input:
- A parsed intent is re-derived through the domain value objects. An invalid runway, an out-of-band frequency, a squawk containing an 8 — any of these and the whole answer is discarded and the local parser's result stands.
- Generated phraseology is checked against the facts the engine approved. Every number in the text must correspond to an approved value. A fluent response containing an altitude the engine never issued is rejected, and the deterministic wording is spoken instead.
See docs/architecture.md.
- Voice-first: push-to-talk in, spoken controller replies out, with a radio-effect audio chain
- Hardware push-to-talk: bind a button on a USB joystick, yoke, gamepad, or HOTAS
- Accent-aware voice trainer: personal keyterms and explicit corrections without storing audio
- Typed fallback: use the complete ATC pipeline without a microphone or cloud account
- Deterministic ATC engine: clearance delivery, ground, tower, departure, centre, approach
- Real readback checking: item by item, with targeted corrections naming the value you got wrong
- Live MSFS taxi routing: airport parking, taxi points, names, paths, runways, and frequencies come from the simulator's Facility Data API; routes begin at the aircraft's live surface position and avoid runway crossings where they can
- VATSIM-style surface training: the dashboard shows the current stand/taxiway, clearance limit, remaining route, next turn, and expected junction sign cues while keeping radio phraseology concise
- Departure ATIS before first contact: COM1 starts on the published ATIS and StormATC speaks the current airport, information code, Zulu time, observed weather, runway, and QNH; the Radio page shows the same facts and continuously loops named cached audio without another synthesis request. Local deterministic comparisons create a new edition only after operational values change; no language model generates or checks ATIS
- Opt-in FSLTL traffic awareness: read moving simulator traffic through SimConnect, identify FSLTL models, and show nearby contacts without controlling or duplicating the traffic injector
- Optional simulated traffic radio: display occasional ATC/pilot exchanges using free local wording, or separately opt in to AI wording and speech with an hourly usage ceiling
- MSFS via SimConnect, connected automatically when the simulator is running, and switched to on its own if you start it later — with a scripted mock aircraft standing in until then
- SimBrief import from inside the app: enter your user ID once and StormATC fetches your latest plan. Nothing to download, nothing to import by hand
- Local-only history: transcripts and sessions live in a SQLite file on your machine
- Protected credentials: API keys are DPAPI-encrypted and can only be sent to the official provider endpoints
- Works with nothing configured: no API keys, no simulator, and no network still gives you a complete, playable ATC session with typed transmissions and deterministic phraseology
- Windows 10 or 11
- .NET 10 SDK to build, or the .NET 10 Desktop Runtime to run
- Optional: Microsoft Flight Simulator with the SimConnect SDK
- Optional: FSLTL for injected live traffic; FlyByWire SimBridge is not required
- Optional: an OpenRouter, OpenAI API, Groq, DeepSeek, or Anthropic account for model-assisted intent interpretation and phraseology
- Optional: a Deepgram account for speech recognition and the controller voice
git clone https://github.com/stormairfly/StormATC.gitcd StormATC && dotnet restore --locked-modedotnet build StormATC.sln -c Releasedotnet test StormATC.slndotnet run --project src/StormATC.DesktopThe first run shows a screen covering scope, cost, and what leaves your computer. Declining the optional cloud services is a supported outcome — the application works fully without them.
Run this once from PowerShell:
.\scripts\Create-StormATC-Shortcut.ps1It creates StormATC (Latest) on the Windows desktop. The shortcut closes this checkout's existing StormATC window cleanly, runs an incremental Release build, and then launches the result. Build failures are shown with paths to local launcher logs instead of opening an old executable.
Keyboard navigation is available throughout the shell: Ctrl+1 through Ctrl+6 opens each page, and Ctrl+, opens Settings.
Nothing has to be configured. Each part decides for itself, and says what it decided:
| Without any setup | Once you set it up | |
|---|---|---|
| Simulator | A scripted aircraft flies the bundled fictional route STMR → STMD | MSFS is connected automatically when it is running. Start it later and StormATC switches over on its own |
| Flight plan | The bundled fictional sample flight | Enter your SimBrief user ID on the Flight Plan page and press import |
| Speaking | Use Typed transmission on the Dashboard | Add a Deepgram key and hold push-to-talk |
| Phrasing | Deterministic phraseology, always available | Choose OpenRouter, OpenAI, Groq, DeepSeek, or Anthropic and add that provider's key and model |
Every one of those is independent. Adding a SimBrief ID does not enable any cloud service, and connecting a simulator does not require a key. Nothing contacts anything until you configure it, and there is an Offline mode in Settings that guarantees that regardless of what is configured.
StormATC is free and open source. It has no accounts, no telemetry, and no subscription.
Every optional cloud provider is an independent third-party service. OpenRouter, OpenAI, Groq, DeepSeek, Anthropic, and Deepgram bill their own API accounts according to their current pricing. StormATC does not resell them or make claims about their rates. A ChatGPT subscription does not include OpenAI API usage.
StormATC v0.2 directly supports OpenRouter, OpenAI, Groq, DeepSeek, and Anthropic for language models, plus Deepgram for speech. The provider abstractions remain open to:
- additional cloud speech-to-text and text-to-speech services; and
- local or fully offline speech recognition and text-to-speech, including voices that do not require a Deepgram account.
Every cloud integration remains optional. Users and contributors supply their own provider accounts and API keys; StormATC does not issue, bundle, or share credentials.
Keys are stored by the operating system under your user account, via DPAPI. StormATC:
- never writes a key to
appsettings.jsonor any other settings file - never stores a key in the SQLite database
- never writes a key to a log
- never includes a key in an exception message or a diagnostics export
- never displays a stored key back to you
- stores a key only when you explicitly click Save
- requires explicit cloud-services consent before using a key
- refuses to send a key anywhere except the selected provider's official HTTPS endpoint
- disables automatic HTTP redirects on credential-bearing requests
Enter, test, and remove keys on the Settings page. See docs/privacy-and-api-keys.md.
- Transcripts and session history are stored on your computer only, in
%LOCALAPPDATA%\StormATC\stormatc.db. Clear them at any time from Settings. - The microphone is open only while push-to-talk is held. StormATC never listens continuously.
- Raw microphone audio is never written to disk.
- With no keys configured, nothing leaves your machine at all.
- With Deepgram enabled, held-PTT audio goes to Deepgram for transcription and controller text goes there to be spoken.
- With a language-model provider enabled, transcripts and the facts a controller has approved go only to the selected provider.
Settings are layered, lowest priority first:
appsettings.jsonbeside the executableappsettings.{Environment}.json%LOCALAPPDATA%\StormATC\usersettings.json— what the Settings page writes- environment variables prefixed
STORMATC_ - command-line arguments
API keys are read from none of these. See docs/development.md.
Run the repository safety check before every commit or release:
.\scripts\Test-RepositorySafety.ps1To create a normal Windows Setup wizard plus a portable ZIP, install Inno Setup, review the SimConnect licence files supplied with your exact MSFS SDK, and run:
winget install --id JRSoftware.InnoSetup --exact
.\scripts\New-StormATCInstaller.ps1 -Version 0.1.2 -AcknowledgeSimConnectLicenseReviewThe publisher runs the secret scan and full Release tests, requires both SimConnect runtime
files, excludes development configuration and local state, creates a self-contained win-x64
installer and portable ZIP, and writes SHA-256 checksums under artifacts/release/.
Microsoft's SDK licence permits distribution only for code it designates as distributable, while the managed SimConnect documentation describes the SDK copy as a build-time reference. Review the licence files installed with your exact SDK version before uploading those Microsoft binaries. The acknowledgement switch prevents doing this accidentally; it is not a legal determination.
The repository also includes locked NuGet dependencies, GitHub Actions CI, Dependabot updates, issue forms that warn against sharing credentials, and a security-focused pull-request checklist. Release binaries are unsigned until the project has a trusted Windows code-signing certificate; do not claim otherwise when publishing them.
The complete first-time repository setup, version-tag, draft-release, artifact-upload, installer, and optional code-signing process is in docs/releasing.md.
src/
StormATC.Domain/ ATC rules, value objects, phraseology. No dependencies.
StormATC.Application/ Use cases, abstractions, the transmission pipeline.
StormATC.Infrastructure/ SimConnect, SimBrief, OpenRouter, Deepgram, SQLite, DPAPI.
StormATC.Desktop/ WPF shell and view models. No domain logic.
tests/ Domain, Application, and Infrastructure test suites.
prompts/ Controller prompts, edited without rebuilding.
data/ Fictional sample aerodromes, flights, and sectors.
docs/ Architecture and setup documentation.
Everything under data/ is fictional. Storm International (STMR), Storm Delta Regional
(STMD), and every coordinate, frequency, runway, taxiway, and stand in them are invented for the
demonstration flight. The ST.. ICAO prefix is not assigned to any real region. StormATC bundles
no real navigation data and none of it may be used for navigation.
| Document | What it covers |
|---|---|
| architecture.md | Layers, the authority boundary, how a transmission flows |
| atc-state-machine.md | Phases, controller jurisdiction, clearance rules |
| prompt-system.md | The prompt files, how they are used, how to edit them |
| simconnect-setup.md | Building with and without the MSFS SDK |
| simbrief-integration.md | Importing a flight plan |
| development.md | Building, testing, configuration, coding standards |
| contributor-quickstart.md | Forking, setup, first changes, and pull requests |
| privacy-and-api-keys.md | What is stored, what is sent, how keys are held |
| releasing.md | Building the installer and publishing a release |
| website.md | Editing, previewing, and deploying the GitHub Pages site |
StormATC is actively looking for co-builders: C# developers, UI designers, testers, documentation writers, pilots, controller enthusiasts, and people with different accents and hardware. Built-in mocks support routine development and testing. Contributors testing live integrations must use their own MSFS installation, hardware, service accounts, and API keys where applicable. The project does not issue or share credentials.
Run one command to verify a new checkout:
.\scripts\Setup-Development.ps1Then read the contributor quickstart, choose a scoped item from the roadmap, and see CONTRIBUTING.md before opening a pull request. Project decisions and the path to becoming a reviewer or maintainer are documented in GOVERNANCE.md.
Use GitHub Discussions for questions and early ideas, Issues for reproducible bugs and agreed work, and SECURITY.md for private vulnerability reporting. Community participation follows the code of conduct.
MIT.