Cirrus Design CORP SR22T accident near Gulf Of Mexico, GM, January 3, 2018

The NTSB's narrative final · quoted from the NTSB record

The pilot was in cruise flight at 19,000 ft mean sea level when he became unresponsive to air traffic control. Military pilots dispatched to intercept the airplane reported that the pilot was seated upright with his head tilted back against his seat and was unresponsive. The airplane continued on its established course at 19,000 ft over the Gulf of Mexico, where radar contact was lost about 3.75 hours after the pilot's last communication with air traffic control. The engine likely lost total power due to fuel exhaustion and the airplane descended into the water. The airplane was equipped with a hypoxia recognition system which was designed to descend the airplane to a lower altitude in the event of pilot incapacitation. Given the altitude of the accident airplane, the system should have activated about 17 minutes after the pilot's last input or interaction with the system. Following the accident, the manufacturer identified a condition under which uncommanded inputs could be made to the airplane's avionics, which could interfere with the normal function of the hypoxia recognition and automated descent features; however, the reason for the accident airplane's continued flight at 19,000 ft could not be determined, as the airplane was not recovered. The last few transmissions by the pilot to air traffic control illustrated a degradation in communication consistent with incapacitation. Given this interaction with the pilot and the lack of response from the pilot when the airplane was intercepted, it is likely that the pilot became incapacitated due to hypoxic hypoxia.

The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.