Learn why runways are elevated or sunken in FSX and fix mesh, scenery-priority, duplicate airport and stale elevation-file conflicts.
Elevated or sunken runways in FSX are caused by a mismatch between an airport’s fixed elevation or flatten polygon and the surrounding terrain mesh, usually after scenery add-ons conflict. Fix the scenery priority, remove duplicate airport files or stale elevation adjustments, then install or create an airport-specific flatten at the correct height.
The same diagnosis applies to boxed FSX and FSX: Steam Edition. Their installation paths differ, but they use the same scenery system. A runway on a plateau is higher than the surrounding terrain; a runway in a trench is lower.
What causes runway plateaus and trenches in FSX?
FSX runway elevation problems occur when two or more scenery components disagree about the airport’s height.
- Higher-resolution terrain mesh: the mesh changes the surrounding ground but cannot automatically correct the fixed elevation of an older airport.
- Duplicate airport BGLs: two airport layouts, commonly called AFCAD or ADE files, may define the same airport differently. AI traffic packages sometimes include these files as well.
- A missing or incompatible flatten: the runway remains at its defined altitude while the terrain rises through it or falls away around it.
- A stale elevation-adjustment file: an old add-on can leave a small altitude BGL in
Scenery\World\scenery, where it may remain active after the main scenery area has been disabled. - An incomplete installation: the airport BGL may be installed without its matching flatten, exclusion or elevation-adjustment file.
FSX’s standard airport system expects a largely flat airport surface. Terrain mesh supplies the surrounding relief, while airport scenery supplies runways, reference altitude and often an airport background polygon. Our explanation of how mesh, airport flattens and scenery priority interact covers that relationship in more detail.
How can I identify the conflicting scenery?
The pattern of the fault usually reveals whether the airport, regional scenery or terrain mesh is responsible.
| Symptom | Likely cause | First check |
|---|---|---|
| One airport changed after installing airport scenery | Duplicate airport BGL or stale altitude file | Disable other files that modify the same ICAO airport |
| Several airports in one region are on plateaus | Regional mesh or incompatible airport data | Temporarily disable that regional package |
| The problem appeared across many countries | Global mesh or a broad elevation package | Test without the newest global terrain layer |
| Only one aircraft floats or sinks | Aircraft contact points rather than terrain | Test the same runway with a default aircraft |
| Buildings float but the runway is correct | Object placement compiled for another elevation | Check for mixed scenery versions |
- Back up the active scenery configuration. Note which airport, regional and mesh packages are enabled before changing anything.
- Isolate the scenery area. Disable one relevant add-on at a time in the FSX Scenery Library, close FSX and restart it so the scenery database can refresh. Do not disable or remove default Microsoft scenery.
- Check for duplicate airport definitions. Look through enabled airport, regional and AI traffic scenery for files affecting the same ICAO code. Filenames often contain the code, but not always, so toggling complete scenery areas is safer than deleting files based only on their names.
- Inspect custom altitude adjustments. If disabling the main airport does not restore the original elevation, check whether that package installed a separate altitude BGL in
Scenery\World\scenery. Move only the identified custom file to a backup folder outside every active scenery directory; never remove an unknown stock file. - Confirm the result. Reload the same airport from the same runway after every change. Once the plateau or trench disappears, re-enable unrelated scenery and leave only the conflicting component disabled.
How do I fix the airport elevation permanently?
The permanent fix is to keep one authoritative airport definition and make its elevation, flatten and surrounding mesh agree.
- Choose the airport scenery you intend to use. If a detailed airport replaces the stock layout, retain that package and disable other add-ons that provide a complete layout for the same airport. Do not try to remove the stock airport from FSX itself.
- Correct the Scenery Library order. Airport and local correction scenery should normally sit above broad regional and global mesh layers; higher entries in the displayed library usually have greater priority. FSX can still select higher-detail mesh from a lower layer, however, so order alone cannot replace a compatible flatten.
- Keep matching files together. Use the airport BGL, flatten or airport background, exclusions and any required altitude adjustment from the same scenery release. Mixing the main airport from one package with an older elevation file is a common cause of persistent trenches.
- Install an airport-specific compatibility patch. Choose this when the airport works without the mesh but fails when that mesh is active. A proper patch retains the intended runway altitude while flattening or transitioning the surrounding terrain appropriately.
- Create a correction when none exists. Airport Design Editor can change the airport reference elevation, define an airport background flatten and compile the required elevation adjustment. Follow our step-by-step ADE airport repair process, and compile the result into a separate custom scenery area rather than editing default FSX files.
Do not change a runway’s altitude merely to hide the cliff. If the airport altitude is correct and the mesh is wrong, correct the terrain transition instead; changing the airport can misalign buildings, parking positions, start points and AI aircraft. A tightly drawn flatten may also leave an abrupt wall, so steep sites sometimes need a wider transition polygon.
A targeted FSX correction using flatten and airport-elevation BGLs shows the type of files used when an airport must be reconciled with SRTM terrain.
Will lowering the FSX mesh resolution fix it?
Lowering Mesh Resolution may hide a runway plateau or trench, but it is a diagnostic test rather than a reliable fix.
If the problem vanishes at a coarser resolution, that confirms the detailed mesh and airport flatten do not agree. Leave the mesh at the resolution expected by your scenery and correct the airport instead. The Mesh Complexity setting does not change the airport’s defined elevation, so adjusting it rarely solves this fault.
Why is the aircraft still floating or buried?
If only one aircraft floats above or sinks into a corrected runway, its contact points or model datum are probably wrong rather than the airport elevation.
Test a default FSX aircraft at the same location. If every aircraft is displaced, look for a duplicate hard runway surface, custom ground polygon or airport BGL at another altitude. If only one add-on aircraft is affected, its aircraft.cfg contact-point geometry needs correction; do not alter the airport to compensate for that aircraft.
After applying the fix, restart FSX and inspect both runway ends, parking positions, AI traffic and the airport boundary. The runway, airport objects and surrounding terrain should now share the intended elevation without duplicate surfaces or abrupt walls.