What happened
Following takeoff, the pilot of a twin-engine airplane was instructed to climb to 16,000 feet. While navigating through heavy snow and instrument conditions, the pilot reported clearing cloud tops at 7,000 feet before receiving clearance to climb to flight level 230. During the subsequent cruise, radar monitoring indicated that the aircraft's course and altitude were inconsistent. Air traffic controllers contacted the pilot multiple times to verify the aircraft's position; although the pilot maintained that the assigned altitude and course were being followed, radar data showed the aircraft repeatedly deviating from its assigned parameters.
Due to the observed altitude fluctuations between FL 224 and FL 237, the controller instructed the pilot to descend to 17,000 feet to exit positive controller airspace. The pilot acknowledged this instruction. Approximately one minute after this acknowledgment, radar showed the aircraft at FL 234. During the final 72 seconds of radar tracking, the aircraft performed a course reversal and descended from FL 233 to FL 214, at which point radar contact was lost. Eyewitnesses observed the aircraft in a spiraling descent accompanied by loud engine noises prior to the impact. There were 0 fatalities reported in the source, though the aircraft was destroyed.
Findings
Post-accident examinations of the engines revealed no mechanical issues that would have prevented standard operation, and investigators confirmed that flight control continuity remained intact. While the investigation explored the possibility that the pilot experienced hypoxia due to the observed altitude deviations and flight profile, the intense post-impact fire prevented an inspection of the pressurization system. Consequently, investigators could not definitively confirm if the pilot's cognitive functions were impaired.