The crash occurred after the aircraft had entered into a steep downward spiral during automated flight at an altitude of 10,600 metres (34,800 ft).

[1] Investigation by Russian Interstate Aviation Committee (IAC) concluded that the crash was caused by a combination of mechanical failure, pilot error and design flaw.

Without proper monitoring, the aircraft managed to enter a heavy turn to the right, spiralling down without any possible recovery and crashed at high-speed.

Following the Soviet Union dissolution in 1991, the aircraft was re-registered as RA-85164 and was sent to Khabarovsk United Air Group, though the livery would not be changed from the former operator.

The crew, who had faced similar situations on prior flights, simply rolled the aircraft's control column to the right to level the wings.

[6] The autopilot, which had been engaged earlier, sensed that the aircraft began to turn towards the right instead, causing the system to deflect the control column to the left.

It eventually reached an angle of more than 30 degree, prompting the aircraft's system to alert the crew on the issue by illuminating the warning lights.

The crew, realizing that the aircraft was in danger of crashing, tried to reduce the list by making a turn of approximately 45 degree to the left on the control column.

[10][11] Radio Moscow initially reported that the wreckage, which was claimed to have been in flames, had been spotted approximately 120 km from Khabarovsk.

[13][10] On 9 December, Deputy Prime Minister of Russia Oleg Soskovets arrived in Khabarovsk to observe and supervise the search and rescue operation.

The Russian Ministry of Defense also announced that they would assist the operation by using satellite imagery, in hopes of finding the wreckage.

Rescuers eventually managed to find some debris before realizing that it had belonged to other airliner accidents that had happened prior to the crash of Flight 3949.

Other reports, which stated that the wreckage had been spotted following the discovery of oil slicks in the north of the Sea of Japan and claims of smoke being seen in Sukpai, were dismissed by officials.

[15][16] Getting desperate after days of no results in finding the crash site, authorities asked the assistance of then-famous Russian clairvoyant Juna, who told them that the search area should have been widened.

[15][10] The crash site was found by chance on 18 December 1995, on the Sikhote-Alin Ridge of Bo-Dzhausa Mountain, by the crew of a Vostok Aviation Company Mil Mi-8 pilot who didn't even take part in the operation.

While making an emergency landing at a taiga, he noticed that the soil on a nearby mountain had different colors than the rest and a part of the fuselage could be seen protruding from the ground.

[7] Later reports suggested that rescuers had flown over the crash site for at least four times but couldn't find it due to inclement weather and rocky terrain.

The crash site suggested that the aircraft had impacted the mountain at a terrific speed, as there were barely any recognizable pieces of wreckage.

The site was strewn with bits of human tissues and personal belongings that had been shredded to small pieces due to the force of the impact.

The crash caused further strain on the industry as, coincidentally, the Federation of Air Traffic Controllers' Trade Union was planning to hold an indefinite worker's strike within a week after.

Russian media Kommersant stated that the then-aviation surveillance system was inadequate and inefficient to handle the industry in the country, which had just been growing exponentially following the dissolution of the USSR.

The aircraft manual didn't specify the actions that the crew should take when such problems occur, and hence said move would be deemed a non-standard procedure.

When the aircraft started to bank to the right, it was unfortunately not noticed by the crew as they didn't think that there was anything wrong and thought that the autopilot was working normally, aggravated by the fact that they were focusing on the pre-landing checklist.

The crew was not trained in handling spatial orientation, which led to Cockpit Resource Management (CRM) breakdown, eventually causing them to be unable to resolve the issue.

[6] The instantaneous banking to the left was attributed to an improperly installed aileron part of the control system of the Tupolev Tu-154.

By the time pilots noticed the failure and filed complaints, the company eliminated those comments and ignored their concerns altogether.

Even though the crew conducted asymmetric fuel transfer, such practice was not considered abnormal as it was common for the operation of the Tupolev Tu-154.

Years before the crash, the Tupolev Tu-154 aircraft had been equipped with an audible alarm that would have alerted the crew on the large bank angle.

It is believed that in order to counteract the left-wing low flying tendency fuel-feed was selected from left wing fuel tanks only.