The commission found that the direct cause of the crash was that the approach was started 4 nautical miles (7 km; 5 mi) too early and that the aircraft therefore came below the height of the terrain. No specific reason for the early approach was found, although there were several non-compliance by the crew members to regulations and procedures. Specifically, the commission pointed to the lack of internal control which would have identified operation shortcomings and the lack of proper cockpit procedures, especially regarding callouts. There were no technical faults to the aircraft, and the pilots had full control of the aircraft at the time of the collision, making it a controlled flight into terrain.
Interviews with random pilots in Widerøe showed that the airline had shortcomings in its training procedures, in part because it lacked a Dash 7 simulator. There was a culture in the airline to divert from cockpit procedures and cooperation. The flight plans often made procedures for mutual control of procedures impractical, and they were commonly skipped. The commission was of the impression that Widerøe's transition from an all-Twin Otter airline to also operate the more demanding Dash 7 was not properly carried out, which had resulted shortcomings in the training and operating procedures. All checklists during the flight were followed correctly. However, the pilots did not elect a method of double-control of the decent and approach, such as by using briefings and callouts.
The pilots had several non-compliances to regulations in their descent. This included using "Torghatten" during the captain's briefing, despite no marking on the map using this name, nor one being located close to the mountain. The aircraft was supposed to have flatted out at 750 meters (2,500 ft), but instead this took place at 500 meters (1,500 ft). The next descent was started at 8 nautical miles (15 km; 9 mi) instead of 4 nautical miles (7 km; 5 mi) from the airport and the aircraft thus came under permitted altitude.
The aircraft was using instrument flight rules (IFR) and Torghatten was covered in fog. The visibility was within the permitted range of IFR. The commission found five errors on Widerøe's maps which could have influenced the accident. This included a formulation which gave the impression that DMR was not in use; a closed "Torget" marker beacon was still on the maps; a vertical flight plan from Lekan was not included; the height limitations in the accident area were noted through comments rather than through a graphical presentation; and confusion as to when the timing of final approach should start. The commission also criticized the airline for its checklists instructing the pilots to one of VHF channels to the company frequency during descent, at a time when non safety-related communication is unwanted.
Because the aircraft was fully booked, a passenger was allowed to sit in the jump seat in the cockpit. The passenger had no connection with the airline, but was granted permission by the captain via acquaintance in the airline. Several of the other passengers were employees in Widerøe and should—according the airline's rules—instead have been seated there. From Namsos to Brønnøysund there were available seats in the cabin, but the jump seat passenger continued to sit in the cockpit. The commission felt that the passenger's conversation with the captain drew his attention and concentration away from his duties at a critical point of the flight. This also disrupted communication between the two pilots, resulting in the mutual control being disrupted.
Read more about this topic: Widerøe Flight 710