Learn why Microsoft Flight Simulator 2004 is called FS9, what the number means, and how FS9 labels affect executables, config files and add-ons.
Microsoft Flight Simulator 2004 is called FS9 because it is the ninth major version in Microsoft’s original Flight Simulator series. “FS2004” is the product name, based on its intended edition year, while “FS9” is the internal version shorthand reflected in files such as fs9.exe and FS9.cfg.
What do FS2004, FS9 and A Century of Flight mean?
These three names describe the same simulator from different angles.
| Name | Meaning |
|---|---|
| Microsoft Flight Simulator 2004 | The retail product name, commonly shortened to FS2004. |
| FS9 | The simulator’s major software generation, version 9.0, and its usual add-on compatibility label. |
| A Century of Flight | The subtitle marking the centenary of powered flight from 1903 to 2003. |
FS2004 was released in 2003 despite the year in its name. Our explanation of the simulator’s release date and naming history covers that apparent mismatch in more detail.
The numbering follows the preceding generations: Flight Simulator 2002 was FS8, while Flight Simulator 2004 moved to version 9. The later Flight Simulator X belongs to the version 10 generation, although simmers normally call it FSX rather than FS10.
Why do the program and configuration files say FS9?
The program and configuration files use the software version rather than the retail year. The main executable is fs9.exe, while the principal settings file is FS9.cfg.
This is also why the default installation folder may be named Flight Simulator 9. If an add-on installer asks for the “FS9 directory”, it means the main FS2004 folder containing fs9.exe. It is not asking for a separate simulator.
A mistake we see regularly is renaming fs9.exe to match the FS2004 branding. Do not do this: installers, shortcuts and utilities may look specifically for that executable name. Likewise, the configuration file should retain its original name; see where Windows stores FS9.cfg if you need to edit or rebuild it.
Is FS9 the same as FS9.1?
FS9 names the simulator platform, while FS9.1 identifies an updated installation of that platform. The official update changes the software version from 9.0 to 9.1; it does not turn FS2004 into a different simulator.
Some add-ons require the 9.1 update, particularly when they depend on updated simulator files. A package described only as “FS9 compatible” is intended for FS2004, but its documentation may still specify whether the update is required.
Will FS9 add-ons work in Microsoft Flight Simulator 2004?
Yes. An aircraft, panel, gauge or scenery package labelled FS9 is intended for Microsoft Flight Simulator 2004.
- FS9 and FS2004 are interchangeable compatibility labels.
- FS8 or FS2002 add-ons belong to the previous generation and are not guaranteed to work correctly.
- FSX add-ons target the successor and should not be installed in FS2004 unless the developer explicitly provides an FS9 version.
- FS9.1 required means the official FS2004 update must be installed first.
This naming convention is used throughout our guide to finding compatible FS2004 aircraft and scenery. If a package offers separate FS9 and FSX editions, choose FS9; our breakdown of the differences between FS2004 and FSX explains why their add-ons are not automatically interchangeable.