Mastering Multiplayer Flights in FSX: A Complete Setup Guide

Microsoft Flight Simulator X (FSX) remains a cherished platform for virtual aviation, even years after its release. While solo flights offer their own rewards, the multiplayer mode opens up a world of shared experiences—flying formation with friends, coordinating cargo hauls, or simply chatting as you cross virtual oceans. Setting up multiplayer in FSX, however, can be tricky due to older network protocols, router configurations, and varying add-ons. This comprehensive guide walks you through every step, from configuring your network settings to troubleshooting common issues, so you can get airborne with others quickly and reliably.

Prerequisites and Preparations

Before diving into configuration, ensure you have the basics covered. You will need:

  • A valid copy of Microsoft Flight Simulator X – either the original retail release or the Steam Edition (FSX:SE). The steps are largely identical, but note that FSX:SE can also leverage Steam’s built-in multiplayer system for easier connections.
  • A stable internet connection – a wired Ethernet connection is preferred over Wi-Fi to reduce latency and packet loss.
  • Router admin access – you will need to configure port forwarding, so know your router’s login credentials (typically found on a sticker on the router or in its manual).
  • Optional but recommended: a voice chat application such as Discord or TeamSpeak, and up-to-date scenery and aircraft add-ons to avoid compatibility issues.

If you are using FSX: Steam Edition, you can skip the port-forwarding steps by using Steam’s invite system. However, for direct IP connections or LAN play, the guide below applies to both versions.

Step 1: Configure FSX Network Settings

Launch FSX and navigate to Settings > Network. Make sure the box labeled Allow Multiplayer is checked. This tells FSX to accept incoming connections from other players. Below that, you will see fields for your Player Name and Call Sign – set these to something unique and recognizable.

Next, click the Multiplayer Options button. Here you can choose your preferred connection type:

  • LAN – for local network games (players on the same home network or a VPN).
  • Internet – for direct IP connections over the internet.

Select Internet for most online games. Note that the Session Name you enter here will be the name others see when browsing (though in FSX, browsing over Internet is unreliable; direct IP is the standard). Leave the port at the default 6112 unless you have a specific reason to change it.

Port Forwarding on Your Router

This is the most common hurdle. FSX uses UDP port 6112 to establish and maintain multiplayer sessions. If your computer is behind a router (which it almost certainly is at home), incoming connection requests on that port must be forwarded to your PC. Here’s how to do it:

  1. Find your local IP address – Press Windows Key + R, type cmd, and press Enter. In the command window, type ipconfig and look for IPv4 Address (e.g., 192.168.1.105). Write it down.
  2. Access your router’s admin panel – Open a web browser and enter your router’s gateway IP address (often 192.168.1.1 or 192.168.0.1). Log in with your username and password.
  3. Find Port Forwarding settings – This menu is often under Advanced > Port Forwarding, Security > Port Forwarding, or Applications & Gaming > Port Range Forwarding. The exact wording varies by router manufacturer.
  4. Create a new rule – You will need to provide:
    • Service Name: FSX Multiplayer
    • Port Range: 6112 to 6112
    • Protocol: UDP
    • IP Address: your local IP address (from step 1)
    • Enabled: Yes
  5. Save the rule and reboot the router if prompted. Many routers also require you to set a static IP on your computer so the address does not change. You can do this in Windows Network Settings, or simply assign a DHCP reservation in the router.

If you are unsure how to access your router, visit PortForward.com and select your router model for step-by-step instructions. Note: some ISPs block port forwarding on their modems/routers; you may need to contact them to request a public IP or use a VPN LAN service (see below).

Firewall Exceptions

Windows Defender Firewall (or any third-party firewall) can block FSX’s multiplayer traffic. To avoid this, add exceptions:

  1. Open Windows Security > Firewall & network protection.
  2. Click Allow an app through firewall.
  3. Click Change settings (you may need admin rights), then Allow another app.
  4. Browse to your FSX installation folder (default: C:\Program Files (x86)\Microsoft Games\Microsoft Flight Simulator X\) and add fsx.exe.
  5. Ensure both Private and Public boxes are checked for FSX.
  6. Repeat for SimConnect.exe if present (usually in the SDK folder, but not required for basic multiplayer).

If you use a third-party firewall, consult its documentation to allow UDP traffic on port 6112 for FSX.

Step 2: Hosting a Multiplayer Session

Once your network is configured, you can host a flight for others to join.

Creating the Session

  1. From the FSX main menu, select Multiplayer > Create a Multiplayer Session.
  2. Choose Internet as the connection type (or LAN for local games).
  3. Enter a Session Name that describes your flight (e.g., “Sunday Group VFR over Seattle”).
  4. Set a Maximum Players (1–32). Keep in mind that more players can increase network load.
  5. Under Session Options, you can control:
    • Direct Connect – If enabled, players can join using your IP address directly. If disabled, they must find you via FSX’s built-in browser (which often fails). Enable this.
    • Room Password – Optional, but recommended for private flights.
    • Allow Shared Cockpit – Allows one player to act as co-pilot in another’s aircraft (requires compatible add-ons).
  6. Click Create Session. FSX will now listen for incoming connections on port 6112.
  7. Your public IP address is required for others to connect. You can find it by searching “what is my IP” on Google. Share this IP with your friends, along with the port if you changed it (default 6112).

Setting Session Environment

Before starting the flight, configure the weather, time, and location. FSX defaults to the host’s settings, but you can allow clients to use their own weather via the Multiplayer Options in the session lobby. For a synchronized experience, set the season and time to match everyone’s time zone or a common night-flying session.

Step 3: Joining a Multiplayer Session

Joining is simpler than hosting, provided you have the host’s IP address and the session is properly forwarded.

Direct IP Connection

  1. From the FSX main menu, select Multiplayer > Join a Multiplayer Session.
  2. Choose Internet and select Direct Connect.
  3. Enter the host’s public IP address in the Host IP field. If the host changed the port, append a colon and the port number (e.g., 203.0.113.5:6112).
  4. If a password was set, enter it.
  5. Click Connect. You should see the session lobby and a list of currently connected players after a few seconds.

If the connection fails, first verify that the host’s IP address is correct and that their router’s port forwarding is active. Also ensure you are both using the same version of FSX (e.g., both on Service Pack 2 or both on Acceleration). Version mismatches are a common cause of silent disconnection.

Alternative: Using the FSX Browser

The older FSX Scan for Sessions feature (sometimes called the session browser) rarely works over the internet because it relies on a deprecated Microsoft master server. For LAN games, it can work, but for internet games, rely on direct IP.

Step 4: Verify Connection and Start Flying

Once connected, you will appear in the multiplayer lobby. The host can see all players and chat. Check the in-game multiplayer status (usually a small icon near the clock or in the top-right corner) to confirm that packets are being exchanged—look for a green indicator. If you see a yellow or red connection symbol, latencies may be high. Briefly test by having the host taxi a few feet; other players should see the movement.

Now select your aircraft and airport. In multiplayer, each pilot flies their own aircraft independently unless shared cockpit is enabled. You can see all other aircraft in the world as long as the models are compatible. If you see a default aircraft where an add-on should be, that means the other player’s model is not installed on your system. FSX substitutes a default model. For best results, agree on a common aircraft and scenery set.

Alternative Solutions for Difficult Networks

If port forwarding seems impossible (corporate network, restrictive ISP, CG-NAT), consider these workarounds:

  • VPN LAN services – Tools like Hamachi (by LogMeIn) or ZeroTier create a virtual local network between your computers. You then select LAN in FSX multiplayer instead of Internet. This bypasses port forwarding entirely because the VPN handles the routing. This is often the easiest method for small groups.
  • FSX:SE Steam multiplayer – If you own the Steam Edition, you can bypass all network configuration by using Steam’s game invite system. From the FSX:SE main menu, select Multiplayer > Steam and invite friends from your Steam friends list. This works seamlessly for groups up to 16 players.
  • Third-party network tools – Add-ons like FSX Multiplayer Utility or JoinFS provide their own connection methods and often include voice chat, shared cockpit, and better reliability. They run as external programs and communicate with FSX via SimConnect.

For more on VPN LAN setups, see this AVSIM guide.

Troubleshooting Common Multiplayer Issues

Even with proper configuration, issues can arise. Here are the most frequent problems and their fixes.

Connection Fails Immediately (“Could Not Connect”)

  • Check that the host’s port forwarding is correctly configured and that the local IP hasn’t changed. Reboot the router and computer.
  • Temporarily disable Windows Firewall to test if it is blocking the traffic. If the connection works, add a proper exception as described earlier.
  • Ensure the host’s PC has a static IP, otherwise the port forwarding rule becomes invalid after a DHCP renewal.

Players Visible but Aircraft Not Moving

This usually indicates a packet loss or high latency. Have the host check their network – running a speed test and pinging the client can reveal issues. Close any bandwidth-heavy applications (streaming, downloads). Lowering graphics settings on all clients can also reduce network load.

“Different Version” Error

FSX versions: base FSX, Service Pack 1, Service Pack 2, Acceleration pack, and Steam Edition are all slightly different. All players must have the same version. For vanilla FSX, apply SP2 (free from Microsoft). For FSX:SE, ensure everyone has the same build (Steam updates automatically). If someone has a third-party mod that changes core DLLs, it can also trigger this error.

Unable to See Other Players at All

This can happen if the host has Direct Connect disabled. Re-create the session with that option enabled. Also verify that all players have the same time zone offset set in FSX multiplayer options (it should be “Use System Time” for simplicity).

Enhancing Your Multiplayer Experience

Once you have a stable connection, consider these additions for a richer experience.

Voice Communication

Typing while flying is impractical. Use a free voice chat program like Discord or TeamSpeak. Create a server for your group, assign voice channels for different flights, and set push-to-talk to avoid broadcasting engine noise.

Shared Cockpit and Add-ons

If you want one pilot to handle flight controls and another to manage radios and navigation, consider using Shared Cockpit mode (host must enable it) along with an add-on like Fs2Crew or Multiplayer Co-Pilot. These synchronise cockpit controls between two FSX instances.

Scenery and Aircraft Compatibility

To avoid “default grey jet” syndrome, agree on a set of freeware or payware aircraft that everyone installs. Popular choices for multiplayer include the default Cessna 172, the PMDG 737 (if all have it), or freeware from FlightSim.com. Similarly, use the same add-on scenery for airports you plan to fly to; otherwise, one pilot’s elaborate terminal will appear as flat terrain for others.

Final Checklist Before Takeoff

Before pressing Fly Now with your friends, run through this checklist:

  • Port forwarding active and local IP static (host).
  • All players on the same FSX version and service packs.
  • Firewall exceptions configured on both host and clients.
  • Common scenery and aircraft installed or agreed defaults.
  • Voice chat ready and tested.
  • Short test flight (e.g., a 10-minute circuit) to verify everything is working before attempting a long cross-country flight.

Multiplayer in FSX can be finicky, but once set up correctly, it provides some of the most memorable experiences in flight simulation. Whether you are reliving historic routes with friends or practicing formation aerobatics, the effort is well worth it. For further assistance, the AVSIM forums remain a treasure trove of FSX multiplayer wisdom.

Now, file your flight plan, tune your radios, and enjoy the skies together. Happy flying!