A P-3 Orion aircraft departed for a ship surveillance mission at 08:36. Approximately two hours later, it struck a mountain on El Hierro, an island located northwest of its patrol area. The aircraft was operating normally for two hours before impacting, with all engines functional except for one, which was shut down for loiter. Visibility was reduced to 50 meters in rain. The crew, including the navigator, radar operator, and flight engineer, was at the NCO club until 02:00 local. The post-mortem revealed a myocardial infarction in the navigator. The island is located inside the northwest corner of the assigned patrol area, and the crew was unaware of its existence. Possible causes include flight crew alcohol consumption/crew rest prior to flight, supervisory/squadron failure, and flight crew complacency. TSC briefing omission of the three Canary Islands likely contributed to the incident. Weather conditions included fog and rain.A P-3 Orion aircraft departed for a ship surveillance mission at 08:36. Approximately two hours later, it struck a mountain on El Hierro, an island located northwest of its patrol area. The aircraft was operating normally for two hours before impacting, with all engines functional except for one, which was shut down for loiter. Visibility was reduced to 50 meters in rain. The crew, including the navigator, radar operator, and flight engineer, was at the NCO club until 02:00 local. The post-mortem revealed a myocardial infarction in the navigator. The island is located inside the northwest corner of the assigned patrol area, and the crew was unaware of its existence. Possible causes include flight crew alcohol consumption/crew rest prior to flight, supervisory/squadron failure, and flight crew complacency. TSC briefing omission of the three Canary Islands likely contributed to the incident. Weather conditions included fog and rain.