Compare FS2004 (FS9) with FSX on graphics, performance, add-ons, Windows compatibility and realism, then choose the right legacy simulator.
FSX: Steam Edition is the better general-purpose legacy Microsoft Flight Simulator for most new installations, with richer scenery, missions, environmental activity and later-generation add-ons. Choose FS2004, also called FS9, for very old hardware or an established collection of aircraft, panels or scenery that was never converted to FSX.
FS2004 (FS9) vs FSX at a glance
FSX is the more capable platform, while FS2004 demands fewer resources and preserves a mature library of legacy add-ons.
| Area | FS2004 | FSX |
|---|---|---|
| Release generation | Released in 2003 and commonly called FS9 | Released in 2006 and later distributed as FSX: Steam Edition |
| Graphics and world | Simpler terrain, water, autogen and virtual cockpits | Denser scenery, improved water and lighting, plus road, boat and airport traffic |
| Built-in flying | Free Flight, lessons, ATC, traditional flights and a historical-aircraft theme | Free Flight and lessons plus missions, shared-cockpit features and more varied activities, depending on edition |
| Performance | Lower hardware demand and generally higher frame rates | More CPU-intensive, especially with dense scenery, weather, water and traffic |
| Add-ons | Large FS9-era library using older gauges, modules and installers | Large native ecosystem with newer model features, SimConnect and more later-generation utilities |
| Memory | 32-bit, although lighter content often leaves more headroom | Also 32-bit and more prone to memory pressure in heavily modified installations |
| Modern Windows | Legacy disc protection and old installers can prevent installation or launch | Steam Edition is usually easier; boxed releases can have activation, permission and installer problems |
| Multiplayer | Original online matchmaking is no longer available | The original boxed service is gone, while Steam Edition supplies Steam-based multiplayer |
The “2004” in FS2004 is the product year; FS9 identifies its simulator generation. FSX followed three years later, but both retain the architecture and limitations of legacy Microsoft flight simulators.
FSX Standard, Deluxe, Acceleration/Gold and Steam Edition do not contain identical default aircraft and activities. Steam Edition broadly includes Deluxe and Acceleration content, but it remains FSX rather than a graphical remaster.
Which should you use: FS2004 or FSX?
Choose FSX: Steam Edition for a fresh general-purpose installation and FS2004 for a specific FS9-only setup.
- Choose FSX for a fresh start: it offers better scenery technology, missions, more environmental activity, SimConnect-based utilities and easier multiplayer access.
- Choose boxed FSX for a dependency: keep it if you already own it and an older aircraft or utility explicitly requires that edition.
- Choose FS2004 for limited hardware: its lighter engine can run smoothly on computers that struggle with dense FSX scenery and traffic.
- Keep FS2004 for irreplaceable add-ons: an aircraft, panel, scenery package or virtual-airline setup may never have received a dependable FSX conversion.
A mistake we see constantly is choosing solely from default frame rates and only later checking the required aircraft or utility. List the add-ons you intend to use first, then confirm whether each requires FS2004, boxed FSX, Steam Edition or a particular FSX expansion.
For a new FSX installation, our guide to buying and downloading FSX legally explains the legitimate editions and acquisition options.
Do FS2004 add-ons work in FSX?
FS2004 add-ons are not reliably compatible with FSX, even when an aircraft initially appears to load.
- Aircraft: some FS9 models work as port-overs under FSX’s DirectX 9 renderer, but animations, lights, sounds and panel gauges may fail. DirectX 10 Preview can produce opaque propellers, missing textures or invisible model parts.
- Scenery: a simple scenery file may display, while old coastlines, terrain flattens, exclusions, airport elevations and object libraries can create duplicated or misplaced features.
- Installers and modules: legacy installers may search for the wrong registry entry or install gauges and modules that are incompatible with 64-bit Windows. The files themselves can still be usable when the installer is not.
- Reverse compatibility: native FSX aircraft and scenery do not normally work in FS2004.
The simulators use different aircraft folder structures, model features, gauge systems, scenery compilers and module interfaces. Copying an entire FS2004 Aircraft folder into FSX is not a dependable conversion method.
Check that every package explicitly names the intended simulator. We keep FS2004 aircraft, scenery and utilities separate from our FSX aircraft, scenery and utility downloads to reduce wrong-version installations.
FSX editions add another compatibility check. Conventional aircraft and scenery often work in Steam Edition, but DLL-based utilities, old installers and products that expect boxed-FSX registry entries may require manual handling.
How well do FS2004 and FSX run on Windows 10 or 11?
FS2004 usually delivers higher frame rates, but FSX: Steam Edition is generally easier to establish on Windows 10 or 11.
FS2004 can install successfully and then refuse to launch because Windows blocks its legacy disc-protection driver; compatibility mode cannot restore a blocked driver. Boxed FSX uses a different activation system but can still encounter activation, protected-folder and obsolete-runtime problems. Steam Edition removes the physical-disc workflow, though individual add-ons may still expect a boxed installation.
What is the safest way to build either installation?
A clean base simulator followed by incremental testing prevents most difficult FS2004 and FSX failures.
- Confirm the required edition. Check every essential aircraft, scenery package and utility before installing the simulator.
- Choose a practical folder. Where the edition permits it, use a dedicated simulator or Steam library outside
Program Filesto reduce permission and VirtualStore confusion. - Apply only the correct updates. Bring FS2004 to its 9.1 update level and boxed FSX to the appropriate final service-pack or Acceleration level. Do not apply boxed-FSX service packs to Steam Edition.
- Run the clean simulator once. Confirm that it launches and allow it to create its configuration files before adding anything.
- Install required legacy components properly. Obtain the applicable DirectX components from Microsoft rather than replacing random DLL files from untrusted sources.
- Add and test packages incrementally. If a failure appears, remove the last addition instead of reinstalling everything. Avoid enabling several compatibility options at once, which makes diagnosis harder.
Both simulators remain heavily dependent on main-thread CPU performance, so a powerful graphics card cannot remove every bottleneck. Maximum autogen, water, road traffic, AI and scenery settings can overwhelm FSX even on much newer hardware.
Both are also 32-bit applications. Complex aircraft, high-resolution textures, large airports and heavy AI traffic can exhaust their address space, with FSX particularly vulnerable when several demanding add-ons are combined.
Is FSX more realistic than FS2004?
FSX has a higher technical ceiling, but it is not automatically more realistic than FS2004.
The aircraft’s flight model, systems, gauges, sounds and documentation matter more than the product year. A detailed FS2004 airliner can simulate systems more deeply than a default FSX aircraft; when comparing equally well-made native add-ons, FSX benefits from newer model features, SimConnect integration and a richer visual environment.
Can FS2004 and FSX be installed together?
Yes. FS2004 and FSX use separate executables, configuration files and scenery databases, so keeping both is often the best answer for an established FS9 user who also wants FSX.
Keep their aircraft, gauges, scenery and add-on directories separate. Old auto-installers frequently guess the wrong target, so verify the displayed simulator version and folder rather than allowing one simulator’s files to overwrite the other’s.
If you want only one, use FSX: Steam Edition on a reasonably capable PC. Choose FS2004 when the computer is genuinely old or a valued FS9-only collection matters more than FSX’s improved scenery, missions and later-generation utilities.