The Civil Aviation Authority (CAA) and its practices have been scrutinised on the final day of the inquest into the Fox Glacier air disaster.
Coroner Richard McElrea has been hearing evidence all week about what caused Skydive New Zealand's Fletcher FU24 aircraft to crash soon after take-off on September 4, 2010, killing all nine people on board.
The inquest has been told there were deficiencies in the CAA flight manual. Manuals were rarely audited and operators were able to have planes modified and signed off by aircraft engineers without the CAA's acknowledgement.
At the time of the crash, skydive operators were not required to be certified.
CAA general aviation manager John Lanham said the CAA was aware of the anomaly with skydive operators, but the Parachute Industry Association (PIA) "strongly objected" to having to comply.
To his knowledge, the PIA viewed skydiving and parachuting as a private operation, which did not require certification.
Operators were also reluctant to introduce restraints for passengers who were parachuting or skydiving as this was considered an unsafe practice in the industry, he said.
New requirements surrounding the safe transport of passengers for skydiving tourism were introduced in May this year.
The Transport Accident Investigation Commission blamed the crash on the plane being overweight and unbalanced. The inquest has also heard evidence that the plane's wrongly set trim caused its steep ascent and skydivers to slide aft, with the weight shift causing the pilot to lose control.
But Mr Lanham discounted all those theories, saying on Friday the cause of the crash was unknown.
Pilot Chaminda Senadhira, dive-masters Adam Bennett, Michael Suter, Christopher McDonald and Rod Miller, and tourists Glenn Bourke from Australia, Patrick Byrne from Ireland, Annita Kirsten from Germany and Brad Coker from England died in the crash.