It is not necessary to file a flight plan via Air Traffic Control (ATC). However, doing so will allow the ATC to vector you through the filed flight plan. And to delete an FMS flight plan, all you have to do is enter a new destination airport, which totally clears the flight data in the FMS. If you have any further questions, please let me know! Best of luck and happy flying!! -TwelveYearOldPilot