The aircraft's takeoff was not observed from the uncontrolled airport, and the aircraft's owner/pilot did not receive any services from air traffic control during the accident flight. When the pilot's son, who was on board the aircraft, failed to return home, his family became concerned and a search commenced. Three days later, his body washed up on a Pacific Ocean beach, about nine miles south of where the aircraft had been based and was last observed. Near the body, a wheel and a seat cushion were also found. The time of the aircraft accident was not determined, no additional wreckage has been located, and the body of the owner/pilot remains missing. Toxicological evidence from the son's body did not indicate the presence of cyanide or carbon monoxide poisoning. The father and son occupants of the aircraft both possessed expired student pilot certificates. The aircraft had been maintained on an annual inspection program, and the ELT's battery replacement date was current. No ELT signal was received.