Authorities said they believed the pilot became disoriented while preparing to land at Isparta in southwest Turkey, but further investigation was needed, CNNTurk television and Zaman newspaper reported.
"The primary data suggests the pilot lost spatial consciousness," Zaman quoted an unidentified civil aviation official as saying.
The office of Ali Ariduru, head of Turkey's Civil Aviation Authority, said he was not immediately available to comment on the reports. Atlasjet, the operator of the flight, declined to comment.
Transport Minister Binali Yildirim said investigators would announce their findings by Friday, state-run Anatolia news agency reported.
The Atlasjet MD-83 was flying from Istanbul to Isparta when it crashed early on the morning of Nov. 30, killing 50 passengers and seven crew members.
Authorities said the plane was off its flight path when it crashed. The wreckage was found 11 kilometers (7 miles) from the airport, on a mountain around 1,500 meters (5,000 feet) high.
Zaman and another newspaper, Yeni Safak, said studies showed the cockpit voice recorder was not recording before the crash while the flight data recorder had little usable data. However, CNNTurk said the recorders were working properly.
Officials had said there was no indication of sabotage in the disaster, which occurred in good weather minutes before the plane was scheduled to land.
Atlasjet, a private airline established in 2001, operates regular flights inside Turkey and chartered flights to Europe and other foreign destinations.
The choice of the city of Helsinki is not incidental as the capital of Finland had hosted US-Soviet negotiations on the limitation of nuclear stockpiles in 1969