The Transport Accident Investigation Commission has backtracked on some of its main findings on the 2010 Fox Glacier sky diving plane crash which killed nine people including four overseas tourists.
The original report from the Commission said that the weight and balance of the aircraft was the most likely cause.
But a new TAIC addendum to the report has just been released, which says that's changed and the aircraft was probably controllable before the crash.
Eight parachutists and the pilot died when the Walter Fletcher plane plunged to the ground on 4 September 2010. Four tourists - from Ireland, Australia, Germany and England - were among those killed.
The commission also said that its decision to allow key parts of the plane wreckage to be buried, just three days after the crash, had limited its ability to determine the true cause of the accident.
The review said that the possibility of a mechanical failure could not be ruled out, but the state of the control structure parts, which were buried for three and half years, was such that the true cause may never be found.
The commission said in the review that additional damage to the plane wreckage was caused by it being moved by three times during the course of the investigation.
Serious questions about the conduct of the investigation were raised at the inquest into the crash.
Independent air crash investigators highlighted a number of problems with the investigation and its original conclusions.
Overseas relatives of the crash victims have also been highly critical of the Commission's handling of the crash investigation.
The father of one victim, Chris Coker, called today's investigation review a "betrayal". Mr Coker's son Bradley died in the accident.
RNZ's Queenstown report, Peter Newport has been following this story and was part of the team that dug up the aircraft wreckage last year.