The US company that makes a helicopter model involved in 18 deaths in New Zealand says the accident rate here is significantly higher than other parts of the world
There are about 300 Robinsons registered in New Zealand, making up about 40 percent of the country's helicopter fleet.
The commission and the Civil Aviation Authority (CAA) has investigated 14 "mast-bumping incidents", where the main rotor blades hit the cabin, causing the helicopter to break up in the air, since 1996.
The California-based Robinson Helicopter Company said it had been trying to understand why this type of accident was so prevalent in New Zealand.
It ruled out terrain and high wind as factors, as similar environmental conditions existed in other parts of the world.
It said its investigations revealed that some training techniques in New Zealand did not match up with those recommended by the company, or US authorities.
The company said it was working with TAIC, the Civil Aviation Authority and flight instructors to fix that.
It said it firmly believed in the safety and reliability of its helicopters.
TAIC raised concerns about Robinson helicopters earlier this year, in a report into a fatal crash near Queenstown in February 2015.
Pilot Stephen Combe was training James Patterson-Gardner when their Robinson R44 broke up in mid-air and crashed, killing them both.
In the report, TAIC said there had been "many other fatal mast-bump accidents involving Robinson helicopters in New Zealand and around the world that have gone largely unexplained".
"It is difficult to identify the lessons from an accident and make meaningful recommendations to prevent similar accidents if the underlying causes cannot be determined," the report said.
"This is a serious safety issue that the industry, including pilots, operators, the manufacturer and the regulator, will need to address."
In response to that report, the victims' families said despite the CAA introducing stricter rules for Robinson R44 helicopters, the model should not be certified to fly.
They said if the men had been in any other aircraft type the accident would not have happened.
"We see a disproportionate accident and kill rate in Robinsons compared to any other aircraft which must be addressed."