If you use PocketFMS for your flight planning/gps then you can:
1. Plan your flight in PFMS, then from within PFMS, select the "Views" button and then the "Google Earth-Plan" report.
This will cause Google Earth to open up with your flight plan shown.
2. Any point on the PocketFMS map that interests you can be quickly seen in Google Earth by simply right click the point on the map in PocketFMS and selecting "View this location in Google Earth".
There are also reports for looking at your breadcrumb file (where you actually flew) in Google Earth after your flight, and indeed this can be shown along side your planned route to see how close you came.
If you are learning to navigate by dead recknoning, then this is a good way of seeing where things started to wrong in your navigation, if they did
dp