A Big Island glider pilot soared to his highest altitude ever just moments before experiencing a sudden, deadly descent into the side of Mauna Loa, according to a National Transportation Safety Board report released yesterday on the Jan. 16, 2009, air crash.

David Bigelow, 69, a retired Aloha Airlines pilot, lifted off that day from the Waimea-Kohala Airport aboard his single-seat DG-400 sailplane in an attempt to reach 40,000 feet and a new state record for gliders.

The pilot, a member of the Mauna Kea Soaring Club, had set a record of 33,351 feet on April 4, 2008.

The plane's flight recorder recovered from the wreckage showed that Bigelow reached an altitude of 38,360 feet during the last six minutes of the flight, the NTSB report said.

A final report on the probable cause of the crash will be released at a later date. Bigelow's family and flying buddies have said they suspect he may have suffered a problem with his oxygen supply and fell unconscious.

NTSB investigators noted the glider was equipped with two oxygen mask systems and a finger blood-oxygen sensing device.

When Bigelow reached 28,000 to 29,000 feet, he radioed his ground team that he was switching to the mask system used for high-altitude flying, which ups the percentage of oxygen delivered to the mask as the altitude increases, the report said.

When the mask system was recovered from the crash site, it was set to "normal," the NTSB said. Between 30,000 and 40,000 feet, the dial is supposed to be set to "safety" to supply oxygen to the mask at high-altitude air pressures, according to the report.

During the last 3 minutes and 20 seconds of recorded flight data, the ground speed of the glider began rapidly varying between about 75 mph and 150 mph within a period of about 10 seconds. Eight second later, when the glider was at 38,630 feet, its flight path abruptly changed from a series of curves to a straight line, the NTSB report said.

A little more than a minute later it suddenly reversed course approximately 180 degrees and descended almost vertically.

Bigelow's remains were found the next day at the 9,800 foot level of Mauna Loa.

The pilot had more than 50 years of flight experience in commercial aircraft and logged more than 800 hours in gliders, the NTSB said.