Flight Plans
A VFR flight plans can be opened via flight service (either though a phone call, or though a flight service frequency), or through an app like ForeFlight. On IFR flight to an airport with a control tower, the control tower will close your IFR flight plan for you.
Search and rescue procedures are commenced 30 minutes after your expected arrival time, if the flight plan has not been closed.
IFR flight plans are usually deleted from ATC systems 2 hours after the proposed departure time.
DVFR Flight Plans
For VFR flights into the U.S. Air Defense Identification Zone (ADIZ), a Defense-VFR flight plan must be filed.
A VFR flight plan filed inflight makes an aircraft subject to interception for identification. Pilots are urged to file the DVFR flight plan either in person or by telephone prior to departure.