What happened
A cargo flight was underway on a planned one-hour cross-country mission using an autopilot-equipped aircraft type. Shortly after takeoff, air traffic control directed the pilot to fly directly toward the destination at 2,000 feet mean sea level. Following this instruction, the aircraft maintained straight-and-level flight at 2,100 feet, continuing well past the intended destination airport. Approximately 100 miles beyond the destination, an observer noted the aircraft flying at a low altitude before hearing three distinct popping sounds. The aircraft then entered a left bank and began a descent, eventually disappearing below the horizon.
The aircraft struck trees in a 45-degree left bank with a level pitch, coming to a stop in a dense forest. A post-crash fire caused significant thermal damage to the airframe. Despite the damage, inspections of the engines, flight controls, and accessories showed no signs of mechanical failure or malfunction prior to the impact. The fuel selector valves were positioned to the outboard tanks, which aligned with standard cruise procedures.
Findings
Analysis of flight records and fuel consumption rates revealed that the outboard tanks held enough fuel for approximately 70 minutes of flight. At the time of the accident, the flight had lasted roughly 75 minutes, suggesting that the engines lost power because the fuel in the outboard tanks had run out. The fact that the aircraft bypassed the destination airport and continued flying on autopilot until the fuel was depleted suggests that the pilot became incapacitated.
While the pilot's autopsy did not reveal a specific natural disease, the severity of the crash limited the scope of the medical examination. Although toxicology reports showed the presence of THC from prior use, investigators determined this was not a contributing factor as it does not typically cause sudden incapacitation. The specific cause of the pilot's loss of consciousness remains undetermined.