The Transport Accident Investigation Commission (TAIC) has for the first time admitted making a string of mistakes while investigating the 2010 Fox Glacier air crash.
Nine people died when their skydiving plane crashed and burst into flames shortly after take-off.
Investigations by TV3's 3D programme led to an official review, which has found investigators got the cause of the crash wrong, and mishandled evidence.
"Our actions are speaking louder than words," said TAIC Commissioner Helen Cull. "We have said if there is something wrong with the process, let's look at it and let's review it, let's get more resources."
Lack of resources is one issue identified in TAIC's review of the crash – that review was initiated after 3D dug up large parts of the plane when it was revealed investigators allowed crucial components to be buried just four days after the accident.
TAIC now accepts it made mistakes, including that it took 27 hours to get an investigator to the scene, the investigation team was short staffed, the scene examination was "unduly short", and the wreck was released prematurely.
"From day one, every single pilot and aviation I talked to said they had it wrong," says one of the victim's son's, Jake Millar. "They thought they had it right. It took a team of journalists from 3D for them to come and say 'no, you guys do have it wrong'."
"What people can have confidence in is that some gaps were identified and now have been addressed," says Associate Transport Minister Craig Foss.
So what about the cause of the crash?
TAIC originally stated: "The most likely reason for crash was the plane being excessively out of balance".
But now it's changed that, saying balance issues were not the most significant factor.
It said the plane pitched up uncontrollably, but now states the plane was in fact controllable. TAIC also initially ruled out technical defects. The review now says technical defects cannot be excluded.
"When they're burying evidence three or four days after the crash and then saying no technical defects were identified, I think that speaks for [itself]. It's bad practice," says Mr Millar.
"They've completely changed their mind on the cause of the crash," says independent air crash investigator Andrew McGregor.
So what did cause the crash? Well, TAIC says it may never know.
Mr McGregor thinks the crash report should be completely rewritten to reflect that.
"They got the cause wrong, now they are trying to patch it up by adding a bit to the original report," he says. "What they should do is start from scratch, rewrite it, this time compressively in accordance with international best practice guidelines."
The Commission says it won't apologise to the families of the victims – but is taking action to stop any future botch ups, including hiring more investigators and having a default policy of retaining and securing all wreckage and evidence.