To automatically download new scenery files, with terrasync:

 - start fgrun
 - click on "Prev"
 - add a new FG_SCENERY directory where you have write access
   (for example /home/user/.fgfs/Scenery)
 - click on "Terrasync directory" so your newly created scenery
   directory will be used by terrasync
 - click on "Next", then select an aircraft
 - click "Next" twice (skip the "Select a location" menu)
 - activate "Terrasync" on its default port (5505)
 - come back to the "Select a location" menu, click on "Scenery Prefetch"
 - choose the four letter airport code of the place your want to start
   from : http://en.wikipedia.org/wiki/List_of_airports_by_ICAO_code
 - leave the "Log Window" in background
 - click on "Refresh", the airports from the newly downloaded scenery
   should be added to the global list