Trigana Air Service flight 267, an ATR 42-300, was destroyed when it impacted a mountainside near Oksibil Airport in Papua, Indonesia. All 49 passengers and five crew members sustained fatal injuries. The ATR-42 departed Jayapura at 14:22 LT (05:22 UTC) and was expected to arrive at Oksibil at 15:04 LT (06:04 UTC). At 14:55 the pilot made first contact with Oksibil Aerodrome Flight Information Services (AFIS), reporting cruising at 11500 feet over position Ambisibil. The AFIS controller acknowledged the message and instructed the pilot to report when overhead the airport. The pilot reported that they intended to fly a direct left base leg for runway 11. The Oksibil AFIS officer then told the pilot to continue approach and to call when position on final for runway 11. There was no further contact with the flight. The aircraft wreckage was found the next day on a ridge of Tanggo Mountain at approximately 8,300 feet AMSL, about 17 km from the airport. The investigators concluded that the flight crew deviated from the standard approach procedure over mountainous terrain. There was no EGPWS warning nor any other EGPWS callout during the descent. The Oksibil Airport was not provided with the high-resolution terrain data in the database version installed on the accident aircraft’s EGPWS. Additionaly, some pilots within the air operator had experiences that the EGPWS warning became active in a condition that according to the pilots, the warning is not appropriate. These experiences led to the pilot behaviour of pulling the EGPWS circuit breaker to eliminate nuisance of EGPWS warning that considered unnecessary. The investigators could not determine the actual EGPWS CB position during the accident flight. Contributing Factors: 1. The deviation from the visual approach guidance in visual flight rules without considering the weather and terrain condition, with no or limited visual reference to the terrain resulted in the aircraft flew to terrain. 2. The absence of EGPWS warning to alert the crew of the immediate hazardous situation led to the crew did not aware of the situation.