Many of the aircraft created by Project Opensky were designed for FS2004, however will work in FSX with some tweaking.
To get it working, install the aircraft as normal. Once installed, you’ll need to replace the panel and sound folder with that of a default aircraft.
Example: Boeing 737-800
1. Install Aircraft
2. Delete panel and sound folders
3. Copy the panel and sound folders from Default 737-800
4. Paste into Project Opensky aircraft folder.