Introduction to Custom Scenario Creation in FSX

Microsoft Flight Simulator X (FSX) remains a beloved platform for flight simulation enthusiasts, largely due to its flexibility and modding community. One of the most rewarding aspects of FSX is the ability to create custom scenarios—tailored flight experiences that go beyond the default missions. Whether you want to recreate a historic flight, practice a challenging approach, or simply enjoy a specific combination of aircraft, weather, and location, building your own scenario is the key. This guide will take you through the complete process, from understanding the file structure to advanced XML editing and troubleshooting.

Understanding FSX Scenario Files

What Is a Scenario?

In FSX, a scenario is a saved flight state that includes all settings chosen at the moment of saving: aircraft, position, heading, altitude, weather, time of day, and even fuel levels. Scenarios are stored as FLT files (binary) and WX files (weather), often accompanied by an XML file for mission-style scenarios. The default location for user-created scenarios is Documents\Flight Simulator X Files or %USERPROFILE%\Documents\Flight Simulator X Files.

Types of Scenarios

  • Free Flight: A simple saved state with no objectives. You can start, pause, and save at any point.
  • Mission Scenarios: Scripted events with goals, triggers, and AI interactions. These use the mission system XML.
  • User-Created Custom Scenarios: Mix of free flight and mission elements, edited manually for fine control.

Understanding these types helps you decide how deep you want to go. For most users, starting with a Free Flight save and expanding via XML editing is the easiest path.

Preparation and Tools

Essential Software

  • FSX with Service Pack 1 or 2 installed – ensures stability and updated file formats.
  • A reliable text editor – Notepad++ or Visual Studio Code for XML syntax highlighting.
  • FSX SDK (optional) – for advanced mission creation. The SDK includes documentation and tools like the SimProp compiler.
  • Weather editing tools – Active Sky or freeware weather editors to craft precise conditions.

Back Up Your Original Files

Before making any changes, copy the entire Flights folder from your FSX installation (Program Files (x86)\Microsoft Games\Microsoft Flight Simulator X\Flights) to a safe location. Also back up your user saved flight folder. This prevents corruption and lets you revert if something goes wrong.

Step-by-Step: Creating a Basic Custom Scenario

Step 1: Set Up Your Flight in FSX

  1. Launch FSX and select Free Flight.
  2. Choose your aircraft (e.g., Cessna 172, Boeing 737, or an add-on aircraft).
  3. Pick a departure airport. For this tutorial, we’ll use KSEA (Seattle-Tacoma International) as an example.
  4. Configure weather: you can select a preset (Clear Skies, Stormy, etc.) or manually set layers.
  5. Set the time of day – sunrise, sunset, or any specific hour.
  6. Click Fly Now and let the sim load.

Step 2: Position Your Aircraft Exactly

Once in the cockpit, you can taxi to a specific runway, take off, or remain at the gate. Use the Slew Mode (press Y) for precise positioning if needed. For a scenario starting airborne, climb to your desired altitude and heading. Pause the sim at the exact moment you want to save.

Step 3: Save the Flight as a New Scenario

  1. Press Esc to bring up the menu.
  2. Select Flights > Save Flight.
  3. Give your scenario a descriptive name (e.g., “Seattle Night Approach 34R”).
  4. Ensure the Save as default flight checkbox is unchecked (unless you want it to load on startup).
  5. Click Save.

Your scenario is now stored as an FLT file in the user’s Flight Simulator X Files folder. The accompanying WX file contains the weather snapshot.

Editing Scenario Files for Advanced Customization

Understanding the FLT File Structure

FLT files can be opened with a text editor (but they are binary – you may see garbled data). For text-based editing, use the corresponding XML file if you created a mission scenario, or convert the FLT to a mission file using the SDK. However, the simplest advanced method is to edit the WX file (which is plain text) and modify the FLT via FSX internal variables.

Replacing Weather via WX File

The WX file contains weather station data. You can manually edit it to change cloud layers, wind direction, visibility, and pressure. Use a weather generator such as FSX Weather Editor or copy weather from a real METAR using FSXWX. After editing, load your scenario in FSX and the new weather will apply.

Creating a Mission-Style Scenario via XML

For complex objectives, create an XML mission file. The SDK provides a complete reference. A minimal mission XML looks like this:

<?xml version="1.0" encoding="Windows-1252"?>
<SimBase.Document Type="Mission" version="1,0">
  <Mission.Title>My Custom Scenario</Mission.Title>
  <Mission.Description>Experience a night approach to Runway 34R at KSEA.</Mission.Description>
  <AircraftSelection>
    <AircraftTitle>Cessna Skyhawk 172SP</AircraftTitle>
  </AircraftSelection>
  <StartLocation>
    <StartType>InAir</StartType>
    <Latitude>47.4480</Latitude>
    <Longitude>-122.3060</Longitude>
    <Altitude>5000</Altitude>
    <Heading>162</Heading>
  </StartLocation>
  <Weather Type="Theme" Theme="Stormy"/>
</SimBase.Document>

Place this file in Flights\missions\mycustom\ and it will appear in the Missions menu. You can add triggers, AI traffic, and scoring using the SDK.

Testing and Debugging Your Custom Scenario

Load and Verify

Open FSX, go to Free Flight, and select your saved scenario from the list (it appears under the "My Saved Flights" section). Fly a few seconds to check everything: position, heading, altitude, weather, aircraft systems. If something is off, note the discrepancy.

Common Issues and Fixes

  • Wrong aircraft: The flight file references an aircraft title. Ensure the exact title matches the aircraft.cfg file. For payware aircraft, titles often include the publisher name.
  • Weather not as saved: FSX regenerates weather on load if the WX file is missing. Ensure the .WX file with the same name as your FLT exists in the same folder.
  • Position inside ground: Altitude may be saved in MSL vs AGL. Use Slew Mode to adjust the aircraft’s exact altitude before saving.
  • Scenario not appearing: Check file extension (.FLT) and that the file is not read-only. Also verify the folder path is user Flights, not the default FSX Flights.

Using FSX Diagnostic Tools

Enable detailed logging in FSX by editing the fsx.cfg file (in %APPDATA%\Microsoft\FSX). Add these lines under [Main]:

  • Logging=1
  • DisablePreload=1

Then check %TEMP%\FSX%USERNAME% for log files. They can reveal errors during scenario loading. For more advanced support, visit FlightSim.com forums or the AVSIM FSX forum.

Advanced Techniques and Best Practices

Adding AI Traffic and Other Aircraft

To include other AI planes in your scenario, you need to edit the traffic file or use the SimConnect API. Tools like AI Traffic Poser can place AI aircraft at specific positions. Alternatively, create a simple flight plan for an AI aircraft and spawn it via FSX's built-in traffic system.

Sharing Your Scenarios

Once your scenario is polished, package it for the community. Include the .FLT, .WX, and any custom .XML or .BGL files. Write a clear readme with installation instructions, credits, and required add-ons (e.g., “Requires FSDT KSEA scenery”). Upload to popular hubs like FlightSim.com or AVSIM Library.

Optimizing for Performance

  • Keep weather complexity appropriate for the aircraft – avoid massive cloud layers that tank FPS.
  • Avoid placing too many AI aircraft or ground vehicles.
  • Use default scenery where possible; add-on scenery can cause mismatches if others don’t have it.
  • Test on a mid-range system to ensure broad compatibility.

Common Pitfalls and How to Avoid Them

  • Saving in mid-air with autopilot on: FSX may desync the autopilot settings. Disconnect autopilot before saving.
  • Weather changes on reload: FSX sometimes regenerates weather for "current time" if the sim clock is changed. Always save with a specific time and weather theme.
  • Missing add-on aircraft variables: When using complex add-ons (e.g., PMDG, A2A), some systems states may not save in the FLT file. Use their native panel state save feature instead of relying solely on FSX scenario save.
  • Incorrect directory permissions: On Windows 10/11, FSX may have limited write access to the Program Files folder. Always save user scenarios to the Documents folder.

For persistent issues, consult the FSDeveloper Wiki, which offers in-depth tutorials on mission creation and SimConnect scripting.

Expanding Your Scenario with Mission Logic

Once you master basic scenario creation, you can introduce objectives: fly a specific route, land within a zone, or complete a search pattern. The mission XML supports <Objective> nodes, <Trigger> zones, and <FailConditions>. For example:

<Objective>
  <Type>FlyToWaypoint</Type>
  <Waypoint>
    <Latitude>47.5</Latitude>
    <Longitude>-122.3</Longitude>
    <Radius>0.5</Radius>
  </Waypoint>
  <CompleteOn>Enter</CompleteOn>
  <Message>Waypoint 1 Reached</Message>
</Objective>

Build a series of waypoints to create a navigation exercise. Use conditional logic to trigger changes in weather, AI traffic, or failures. This is where FSX truly shines as a sandbox for creative scenarios.

Conclusion

Creating your first custom scenario in FSX is a gateway to a massive world of personalized flight simulation. By following the steps outlined above—from basic save to XML editing and troubleshooting—you can craft experiences that suit your training needs, recreate real-world flights, or design challenges for friends. Remember to experiment, back up your files, and engage with the community. The more you build, the more you’ll understand the inner workings of FSX. With patience and practice, you’ll soon be producing scenarios that are not only functional but truly immersive. Happy flying!