A culture exists among some of New Zealand's helicopter pilots of operating their aircraft beyond the published limits, according to the Transport Accident Investigation Commission.
TAIC has listed a number of safety concerns, in response to a 2014 helicopter crash near Mt Aspiring National Park in which one person died.
It's also been studying other similar accidents.
In the 2014 heli-skiing crash, the tourist chopper operated by The Helicopter Line was heading in to approach the landing site on Mount Alta.
Seven people were on board, including five members of a church group.
TAIC Chief Commissioner Jane Meares says: "The helicopter went below the pilot's intended angle of approach, so the pilot turned it away from the ridgeline, but he couldn't avoid the terrain."
On impact, the cabin of the aircraft broke apart and five of the seven people were flung out as it rolled 300 metres down the mountain.
Jerome Box, 52, a member of the church group, became trapped under the aircraft and died.
TAIC says it's "very likely" that several seatbelts worn by the passengers were not securely adjusted, meaning they were more likely to be ejected.
The Commission also found that the helicopter was loaded about 30 kilograms over the maximum permissible weight. The centre of gravity was forward of what is allowed.
Investigations found there were no mechanical reasons for the crash.
In identifying the safety issues, TAIC reports "the operator's pilots weren't routinely required to calculate the performance capabilities of their helicopters for the intended flights".
It also says "there was a risk of pilots not knowing their aircraft's capability when using standard passenger weights, and therefore a risk of exceeding the limits of their aircraft's performance."
Noting that this so-called culture "adversely" affects the safety performance of the industry, TAIC recommends that the Civil Aviation Authority puts this safety issue in its current sector review.
Authorities have announced an investigation is underway after engine "abnormalities" on two separate Air New Zealand flights in the space of two days saw two flights forced to return to Auckland shortly after take-off.
The engine issues both happened on Boeing 787 Dreamliner planes flying out of Auckland bound for international destinations.
The first was an Air New Zealand flight headed for Narita, Japan on Tuesday morning, where the crew shut down an engine and returned to Auckland shortly after take-off.
Last night another Air New Zealand 787, headed to Buenos Aires, Argentina, experienced an engine issue shortly after leaving Auckland and was also forced to return.
In a statement released today the Transport Accident Investigation Commission say they've opened inquiries into both events, with investigators having been on the ground in Auckland since Tuesday.
The commission say they're working closely with Air New Zealand, the Civil Aviation Authority and engine-manufacturer for Boeing Dreamliners Rolls Royce.