The Air Force's inquiry into the chopper crash that killed CDS General Bipin Rawat, his wife and 11 armed forces personnel is almost complete and will be submitted soon, sources told NDTV Sunday.
Neither the Air Force nor the government has made any statement yet on the probe or its report, but sources indicate that reduced visibility due to bad weather may have contributed to the crash.
There has also been no statement or explanation so far on whether pilot-error was the underlying cause of the accident or whether rules for operating within clouds in hilly areas were disregarded.
Sources said the Court of Inquiry - led by Air Marshal Manvendra Singh, the country's top helicopter pilot - believe the pilot of the MI-17v5 that crashed in Tamil Nadu's Nilgiri hills on December 8 may have been left disoriented by inclement weather and accidentally flown into terrain.
This is referred to as CFIT, or Controlled Flight Into Terrain.
Sources also said the inquiry ruled out any possibility of technical errors or mechanical defects.
The inquiry team is currently being advised by the Air Force's legal department in finalising the report, which is expected to be submitted to Air Chief Marshal VR Chaudhari within five days.
Gen Rawat, his wife Madhulika, and 10 armed forces personnel, including Brigadier LS Lidder, the General's top aide, were killed outright after their chopper crashed into Tamil Nadu's Coonoor region.
The General was on his way to speak at the Defence Staff Services College in Wellington.
Group Captain Varun Singh, a passenger on the helicopter, survived the crash but had severe burn injuries, and he died days later while being treated at the Air Force's Command Hospital in Bengaluru.
In the days after the crash mobile phone videos - taken by locals and shared by news agency ANI - emerged of the final moments of the chopper; one clip shows a helicopter flying into the mist that hung over the Coonoor hills and a change in the chopper's engine sound can be heard.
Gen Rawat, his wife, and all those on board were given funerals with full military honours, and thousands paid tribute to their memories, including the governments of major foreign powers.