Fix X-Plane 12's GRIB file not found error by refreshing Real Weather, clearing cached data, checking network access and isolating plugins.
X-Plane 12 shows a GRIB file not found error when Real Weather cannot download, locate or read the forecast file used for winds and temperatures aloft. Refresh Real Weather, clear its cached files, check firewall and system-clock settings, and disable weather injectors. If the provider is unavailable, use manual weather and retry later.
What does the GRIB file error mean?
A GRIB file supplies gridded forecast data rather than airport observations. X-Plane 12 combines that upper-air information with other weather sources, so local conditions can appear plausible even when global winds or temperatures have failed to load. Our explanation of how X-Plane receives and processes real-world weather data covers that distinction.
The missing file is normally downloaded as part of a Real Weather update; it is not an aircraft, scenery or navigation-data file omitted from the base installation. Common causes include an interrupted download, blocked network access, a damaged cache, an incorrect clock, a weather plugin conflict or a forecast cycle that the data provider has not made available.
How do I fix the X-Plane 12 GRIB file not found error?
The reliable approach is to test X-Plane's built-in weather first, then remove each possible obstruction in order.
- Confirm that Real Weather is the trigger. Select manually configured weather and load the flight. If that works, the aircraft and weather engine are functioning; the problem is confined to downloading or reading live data.
- Force a fresh weather request. In the weather panel, switch from Real Weather to manual weather, apply it, then select Real Weather again. Use the refresh control if your X-Plane build displays one. Our Real Weather setup and refresh walkthrough explains the normal controls without repeating them here.
- Correct the date and clock. Enable automatic time, date and time-zone synchronisation in the operating system, then restart X-Plane. An incorrect system clock can break secure downloads or make X-Plane request the wrong forecast period. Do not expect an arbitrary historical simulator date to have matching downloadable data.
- Check network filtering. Allow the X-Plane executable to make outbound secure connections. VPNs, proxies, DNS filters, antivirus web shields and firewall rules can block weather data even when a browser works. Test without the intermediary or on another connection, but do not leave security software disabled.
- Clear the weather cache. Close X-Plane completely. In the X-Plane installation folder, open
Output/real weatherand move its contents to a temporary backup. Do not delete the wholeOutputfolder. Start X-Plane and select Real Weather so it downloads clean copies. - Remove competing weather plugins. Move third-party weather injectors out of
Resources/plugins, rather than merely renaming their folders inside it, and stop any companion injector application. Restore add-ons one at a time after built-in weather works. See our add-on installation and isolation notes if you need help identifying plugin locations. - Repair the installation last. For a direct installation, run the X-Plane Installer and update the existing copy; for Steam, verify the installed files. This can replace damaged default components, but it will not cure a provider outage or a firewall block.
Do not download an arbitrary .grib file and place it in the cache. X-Plane expects compatible forecast cycles, timestamps and naming, so an unrelated file can produce another missing, stale or unreadable-data error.
How can I tell whether the problem is local or an outage?
Log.txt in the main X-Plane folder usually identifies which stage failed. Reproduce the error, close the simulator and inspect the log before launching it again, because a later session can replace the useful evidence.
| Log clue | Likely cause | Next action |
|---|---|---|
| HTTP, DNS, certificate or timeout message | Network filtering or unavailable service | Check the clock, firewall, VPN and another connection |
| Permission denied or cannot write/open | X-Plane cannot write to its installation folder | Correct folder permissions and confirm free storage space |
| File missing, incomplete or unreadable | Broken cache or interrupted download | Clear Output/real weather and retry |
| Weather-plugin entries immediately before the error | Injector conflict or incompatible add-on | Remove all weather plugins, then restore them individually |
| A repeated not-found response after a clean request | Forecast cycle unavailable from the provider | Use manual weather and retry after the next data update |
If a fresh cache, a correct clock and an unfiltered connection still produce a not-found response, reinstalling scenery or aircraft will not help. A missing GRIB download should not normally crash X-Plane; if it does, follow our startup-crash and plugin-isolation process.
Can I keep flying without the GRIB file?
Yes, but select manual weather rather than assuming the partial Real Weather load is accurate. Airport observations may appear while winds and temperatures aloft are stale, absent or taken from a fallback state, which can affect fuel planning, groundspeed and arrival estimates.
For casual flying, a manual preset is the cleanest temporary solution. For online operations or weather-dependent IFR practice, wait until Real Weather completes a fresh update so the simulator's upper-air conditions match the intended session.