At approximation the missing parts opposite are show up.
If you see only parts of an object missing, the problem is entirely related to your video card settings, and if it happens only after a long flight, is due to memory exhaustion and/or bugs in the video driver, or bugs that are triggered by settings and/or tweaks.
Try all the following:
- Update your video driver
- Reset your video driver settings to default
- Reset the FSX settings to default, by removing the following file:
%APPDATA%\Microsof\FSX\FSX.CFG
This will force FSX to rebuild a new config with all default settings. After doing this, be sure you apply the HIGHMEMFIX tweak in the Addon Manager, save the settings and restart FSX.
If this still doesn't fix it, be sure you don't run FSX into any of the "Compatibility" modes. Every checkmark in the Compatibility tab of the Properties for FSX.EXE should be off.