Incident Overview
An air traffic controller observed a nighttime instrument flight rules (IFR) flight operated by a 68-year-old pilot deviating south of its assigned course, correcting slightly, then deviating south again. The deviations reached up to 90 degrees from course, and altitude varied between 14,000 feet MSL and 14,400 feet MSL. Radar contact was lost approximately 10 miles southeast of Helena, Montana, in an area with normally good radar coverage. The aircraft subsequently sustained an in-flight breakup before impacting in hilly terrain.
Flight History
The flight was cleared to climb to 12,000 feet at 1936. At 2006, the controller noted, "I don't know where he's going...he's all over the place." During the on-scene investigation, it was determined that a portable oxygen bottle carried in the airplane was not being used by the pilot. The pilot was known to fly at altitudes above 12,500 feet, and as high as 17,000 feet, without using oxygen.
Medical and Autopsy Findings
An autopsy of the pilot revealed atherosclerosis of the coronary arteries with 90% stenosis of the left anterior descending coronary artery and 90% stenosis of the right coronary artery, as well as multiple blunt force injuries.