An investigation found several shortcomings in the airline's operating procedures, in particular lack of proper cockpit communication and mutual control of the descent and approach plans.

Flight 710 was the second of four Widerøe accidents between 1982 and 1993, all of which revealed shortcomings in the airline's operations and internal control.

The accident aircraft was a four-engine de Havilland Canada DHC-7 Dash 7 Series 102, with serial number 28, built in 1980.

He was hired as a pilot for Widerøe on 6 February 1986, originally serving on the de Havilland Canada DHC-6 Twin Otter.

The aircraft was packed and therefore a jump seat in the cockpit was used by a passenger, bringing the number of people on board to 52.

During the flight, the passenger in the jump seat held a conversation with the captain and asked several questions regarding the operations.

The first officer did not participate in this discussion, and it was he who conducted radio contact with air traffic control and the airline's operations center.

At 20:20:29, the aircraft asked permission from Trondheim ATCC to switch to Brønnøysund Aerodrome Flight Information Service (AFIS), which was granted.

At 20:23:22 the first officer held a 62-second conversation with the airline ordering a taxi for one of the passengers so he could reach his connecting ferry.

The fasten seat belt sign was switched on and the flight attendant started the process of preparing the cabin for landing.

The direction of the VHF omnidirectional radio range (VOR) and distance measuring equipment (DME) at Brønnøysund was checked at 20:26:37.

At 20:27:32 the captain asked for flaps and landing gear, which were immediately deployed by the first officer and resulted in the aircraft gaining 70 m (230 ft) of altitude.

Four seconds later the passenger asked the captain if there were reserve systems which could be used if the landing gear did not deploy properly.

[9] The commission found the cause of the crash was that the approach was started 4 NM (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-compliances by the crew members to regulations and procedures.

[12] 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.

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.

[20] The commission also criticized the airline for its checklists instructing the pilots to tune one of the VHF channels to the company frequency during descent, at a time when non-safety-related communication is unwanted.

[22] 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.

[24] The aircraft crashed into Torghatten, which is located 5 NM (9 km; 6 mi) south-west of Brønnøysund Airport.

It received a call from a resident close to Torghatten which said they had heard aircraft noise followed by a crash.

The investigation commission was later supplemented by psychologist Grethe Myhre and Øverkil replaced by Arne Huuse.

[22] AIBN established a base of operations at the hangar at Brønnøysund Airport and used a helicopter to freight the pieces of the wreck there and bodies to Trondheim University Hospital for identification.

[31] Improper use of the microphone made it difficult to hear the captain's voice, but it was possible to reconstruct the conversations and line of events.

As this had not been mentioned in the original report, AIBN conducted a review of the issue and especially if the telephones could have influenced the vertical navigation.

It was at the time the third-deadliest aviation accident in Norwegian history, after the 1961 Holtaheia Vickers Viking crash and Braathens SAFE Flight 239 in 1972.

[26] The commission recommended that Widerøe update its maps for Brønnøysund, review and improve its landing procedures,[10] improve its internal control procedures to ensure that pilots follow the airline's flight operation regulations, and introduce the Sterile Cockpit Rule.

The commission recommended that the Civil Aviation Administration change the flight paths at Brønnøysund to increase the altitude around Torghatten.

In the first accident, Flight 933, a poor cockpit culture had also been discovered, but little was followed up, in part because of a conspiracy theory which surfaced regarding a collision with a fighter jet.

Several major press organizations attended the memorial service, and newspapers published close-up pictures of crying next of kin on their front pages.