Flightsim planner gives you the ability to use MBTILES formatted maps in offline modes. Preinstalled are the links to the maps from the 
openfilghtmaps project. These charts can be downloaded within the app and used in offline modes after. Additional charts can be added via a special folder that is monitored by the FSP Server V2. The MBTILES files found in this folder are, by request added to the list of maps within the app and can be downloaded. This way you can use any on your pc downloaded MBTILES file. For instance all US sectional charts can be downloaded in MBTILES format from chartsbundle and be used in the app.
This option will replace the custom georeferenced charts. If you have referenced charts using Mapchruncher the FSP server V2 gives you an option to convert these to the MBTILES format.
Other options for creating charts overlays in MBTILES format are
https://www.maptiler.com/desktop/
QGis with QTiles