What happened
A maritime patrol mission departed from Lajes Airport in the Azores Islands at 08:36 local time. Approximately two hours after takeoff, the crew transmitted a status report indicating that the flight was proceeding normally; this served as the final communication from the aircraft.
While cruising at an altitude of 2,300 feet, the four-engine airplane impacted a mountain slope measuring 5,200 feet in height. At the moment of impact, the aircraft was traveling at 220 knots through foggy conditions that significantly restricted visibility. The wreckage was subsequently located within a forested region near La Frontera, situated in the center of the island. During the final phase of flight, the number one engine had been shut down to facilitate loitering, leaving three engines operational.
Findings
Investigations into the accident identified several contributing factors that led to the crash. The crew was operating under conditions of fatigue due to having consumed alcohol until 02:00 and starting the mission without adequate rest. Additionally, there was a lack of effective oversight from authorities regarding aircrew surveillance.
Operational failures also played a role, including crew complacency and a failure to follow standard navigation procedures. It is believed the crew may not have been properly briefed before departure and likely lacked awareness regarding the proximity of Hierro Island. These issues were compounded by environmental factors, specifically poor visibility caused by fog and rainfall.