What happened
A cross-country flight involving the pilot and three passengers proceeded normally until the aircraft climbed past 26,600 feet. At this altitude, the pilot ceased responding to instructions from air traffic control. Tracking data indicated the aircraft type continued to climb to 34,000 feet, following its programmed waypoints and turning southwest to pass its intended destination approximately one hour later. The flight continued for another hour at a steady altitude and track before the aircraft entered a spiraling descent and struck the ground.
Shortly before the descent began, United States Air Force pilots intercepted the plane. They reported seeing no structural damage, no smoke within the cabin, and no deployed oxygen masks. They observed one occupant slumped in the pilot seat with no movement from others in the cabin. All four fatalities were likely the result of the flight's progression into a state of uncontrolled descent.
Findings
Evidence suggests the occupants likely suffered from hypoxia due to a loss of cabin pressurization. While the pilot had medical history involving high blood pressure and cholesterol, as well as access to certain medications, there was no evidence of improper medication use. Instead, maintenance records revealed significant issues with the aircraft's environmental systems. Specifically, several discrepancies related to the pressurization system had been noted by maintenance personnel weeks prior but were left unaddressed by the owner.
Furthermore, just two days before the flight, it was noted that the pilot-side oxygen mask was missing and the supplementary oxygen levels were at the minimum required for service. At this level, oxygen would not have been available to the occupants, and passenger masks would not have deployed during a depressurization event. The lack of response to air traffic control and the observed state of the occupants suggest that altitude-related hypoxia caused the crew and passengers to become incapacitated.