Getting started

Guide

How CrossSim works, how to set up the desktop app, and where to get model libraries so you can see other pilots correctly.

What is CrossSim?

CrossSim links MSFS2024 and X-Plane 12 together in the same multiplayer session, regardless of which simulator each pilot is running. Sessions are created from the CrossSim Desktop app; this website lets you sign in, manage your account, see your sessions, and watch a live map of who is flying.

1. Create an account

Create an account on this website with your name, email, and a password. You'll use the same account to log in from the desktop app.

2. Install the desktop app

Once logged in, go to Download and install the CrossSim Desktop app. It ships already configured to talk to crosssim.fsmissions.com — you don't need to change anything unless you're pointed at a different server (for example a self-hosted relay), in which case use the "Change server" link on the app's login screen.

3. Log in and connect your simulator

Open the app, log in with your website account, and pick your simulator (MSFS2024 or X-Plane 12). Leave the aircraft loaded and active — the app needs an active flight to read live telemetry, so "waiting for flight" means the simulator hasn't reported a flight yet, not that anything is broken.

4. Create or join a session

From the app you can create a new session (you become the owner) or join one with a join code, which the owner can share and regenerate from the website's session page. Once in a session, set your callsign and aircraft in your lobby profile and mark yourself ready.

5. Watch the live map

While a session is active, its lobby page on this website shows a real-time map with every connected pilot's position and heading, updated as telemetry arrives from the desktop app.

Model libraries: MTL and CSL

To see other pilots as their actual aircraft (instead of a generic placeholder), your simulator needs a matching model library installed:

• MTL (Model Traffic Library) is the model-matching format used by MSFS. Community MTL packs (commonly distributed by groups such as IVAO or AIG for MSFS) map aircraft types and liveries to 3D models your simulator already has installed.
• CSL (Custom Scenery/Livery) is the equivalent format for X-Plane, used by online networks like VATSIM/IVAO to render other pilots' aircraft.

You don't need to install anything from CrossSim itself — download an MTL pack for MSFS or a CSL pack for X-Plane from your simulator's usual online-network community (search your sim's forums or the network you already fly on for "MTL" or "CSL" download pages), then point the CrossSim Desktop app at the installed folder from the Model Libraries screen. The app validates the folder and lets you review and fix any aircraft it can't match automatically.

Troubleshooting

If you can't reach the server when logging in, check the "Server" line on the app's login screen — it should read https://crosssim.fsmissions.com. If you don't see other pilots in a session, confirm both sides have an active flight loaded (not sitting on the main menu) and that your model library is configured, since a missing model library affects only the visuals, not whether the other aircraft appears.