This amazing article I found on the AFSS website is a true story and details why it's important to not only file a flight plan but to use common sense when filing/planning. You will get what I mean in the first couple of sentences.
Cheap Insurance: The VFR Flight Plan
A Cessna 172 departed an uncontrolled airport in Somewhere, OK headed to Somewhere Else, CA. The pilot wisely filed a VFR flight plan but unwisely filed only a single flight plan with an en route time of 12 hours. Upon departure the pilot activated the flight plan with a nearby AFSS. The unfortunate aircraft had barely departed the pattern when the engine failed. Not quite clearing a grove of trees, the aircraft then impacted the ground and suffered major damage; the pilot was severely injured and could not escape the cockpit. There were no witnesses to the accident. What happened next?
Search and Rescue (SAR) procedures begin thirty minutes after the Estimated Time of Arrival (ETA). The destination AFSS sends an electronic message to the departure AFSS (flight plan origination) to obtain complete flight plan details. Using the information provided, the destination AFSS, having primary SAR responsibility, then conducts an extensive "communications" search, i.e., telephone and radio. If the destination is a controlled airport, a call to the tower often reveals whether the overdue aircraft has arrived. If there isnít a tower then will request either the airport authorities or the local FBO to do a ramp/hangar check. In some instances a local law enforcement agency will get involved. Unfortunately, many aircraft are put away in locked hangers which often cannot be accessed. If the pilot had the foresight to provide a destination phone number (rather than a home number, for example), the job of locating the aircraft could be quite simple. Many pilots only give a home number which may necessitate a delicate call to their residence − one that may cause unnecessary anxiety.
One hour after ETA, in addition to the ongoing communications search, the destination AFSS transmits a message to multiple Air Traffic facilities (and DUAT vendors) along and 50 miles either side of the intended route, checking for any contact with the airplane. Please read between the lines here. Had the pilot provided periodic pilot reports and/or position reports, then there would be evidence of the flight progress, greatly narrowing the primary search area. At this point in the SAR process, airports along the flight path are also contacted to do physical searches of their airports; a daunting task but much cheaper than an aerial search. Many an airport manager has been called in the middle of the night to drive out to the local grass strip to check hangers with a flashlight.
Two hours past ETA, the Air Force Rescue Coordination Center (RCC) gets deeply involved; air and ground search teams are rapidly organized. The Civil Air Patrol is activated. The cost of the search escalates quickly. Most SAR cases end on a happy note: the embarrassed pilot merely forgot to cancel his/her flight plan. Nevertheless, this typically comes at a high cost of time and labor on the part of many organizations. Search efforts, both on the ground and airborne, can even put search teams in harmís way. The happy note is now the sour note.
Many pilots, usually those that have forgotten to cancel a flight plan in the past, have developed pretty ingenious ways of remembering to cancel a flight plan, such as:
Calling yourself and leaving a voice or text message on your cell phone
Putting a rubber band around a finger or wrist
Wearing your wrist watch on the wrong wrist
Whatever works for you is very much appreciated by those that are part of the SAR process.
Okay, what happened to the C172 that crashed shortly after takeoff? By now you probably have come to an accurate conclusion to this scenario. Because the pilot chose to file a single flight plan with a single 12-hour en route time, the physical search for his downed plane did not even begin until 14 hours after his flight into the trees. If the weather was relatively warm there may be a reasonable chance of survival. In this case, which actually occurred a few years ago, the pilot did not live long enough for rescuers to reach him. It was speculated that, had he filed multiple flight plans (one for each en route fuel stop), the search would have been mounted much sooner and he may have survived. Please remember, even with a functioning ELT, it still takes valuable time to locate a downed aircraft.
Always file a Flight Plan. Always activate the Flight Plan; and always cancel the Flight Plan when you have landing assured or are safely on the ground.
It is the cheapest flight insurance you can own!