The full report (NTSB/AAB-01-02) is available on the NTSB Web site. See http://www.ntsb.gov/Publictn/publictn.htm for details. On September 25, 1999, about 1726 Hawaiian standard time, Big Island Air flight 58, a Piper PA-31-350 (Chieftain), N411WL, crashed on the northeast slope of the Mauna Loa volcano near Volcano, Hawaii. The pilot and all nine passengers on board were killed, and the airplane was destroyed by impact forces and a postimpact fire. The sightseeing tour flight was operating under 14 Code of Federal Regulations Part 135 as an on-demand air taxi operation. A visual flight rules flight plan was filed, and visual meteorological conditions existed at the Keahole-Kona International Airport (KOA), Kona, Hawaii, from which the airplane departed about 1622. The investigation determined that instrument meteorological conditions prevailed in the vicinity of the accident site. A Big Island Air employee who observed the pilot upon his arrival at KOA shortly before 0700 on the day of the accident stated that the pilot appeared to be alert and well rested. The pilot was scheduled to make two air taxi flights that day. The morning sightseeing flight departed about 0700, and the second (accident) flight departed about 1622. The morning's weather report was included on the "Flight Plans and Weather" form that Big Island Air pilots typically reference before flying with an indicated time of about 0700. Big Island Air's Director of Operations reported to National Transportation Safety Board investigators that he had obtained this weather information from the Federal Aviation Administration's (FAA) Honolulu Automated Flight Service Station (AFSS). No evidence exists to indicate that the pilot sought or obtained an updated weather briefing for the accident flight later that afternoon as required by the FAA. The pilot departed KOA about 1622 for his second sightseeing tour of the day and followed a half-island tour route. About 1720, the pilot requested permission from the Honolulu AFSS to transition through a restricted area of airspace (R-3103) that encompasses part of the center of the saddle area. The pilot was advised by AFSS that the restricted area was "open," and he was authorized to transition the area for the next 30 minutes. The FAA did not record any further radio transmissions from the accident pilot. According to FAA-recorded radar data, at 1721:04, the accident airplane was located approximately 16 nautical miles (nm) east-southeast from the eastern side of the restricted area (about 8.5 nms from the crash site). The accident airplane's altitude, as transmitted by its Mode C-equipped transponder, was about 6,600 feet, and the underlying terrain's elevation was about 4,600 feet mean sea level (msl). Both the airplane's altitude and the terrain's elevation were increasing. Between 1721:04 and the last recorded radar return at 1725:29 (when the airplane was within 1/3-mile of the accident site), the airplane's average ground track was approximately 291 degrees, magnetic. During this time, the accident airplane's altitude increased from about 6,600 to 9,600 feet. Several witnesses observed clouds below the 10,000-foot level around the time of the accident. About 1726, the accident airplane crashed on the northeast slope of the Mauna Loa volcano at 10,100 feet msl.