The seaplane that crashed north of Sydney killing six people on New Year's Eve had been "destroyed" in a fatal accident two decades ago, an investigation report shows.
Authorities are trying to determine what caused the plane to plunge into Jerusalem Bay, killing British executive Richard Cousins, 58; his two sons William, 25, and Edward Cousins, 23; his fiancee Emma Bowden, 48; her daughter Heather, 11; and pilot Gareth Morgan, 44.
The Sydney Seaplanes aircraft had flown thousands of trips around Sydney Harbour since the early 2000s.
But the de Havilland Canada Beaver model, first registered in 1964, flew under a different registration in a previous life as a crop duster with the same serial number. The plane set off from Armidale in the state's north on November 15, 1996, and was preparing to spread a load of phosphate fertiliser on a nearby property when it fell into difficulty in hot, gusty winds.
It failed to rise steeply enough, clipped a hillside with a wing and cartwheeled, a government report found.
The pilot was killed, and under "damage to aircraft" the investigators wrote "destroyed". They found that wind conditions, air density and the plane's weight were all significant factors in the crash. But they could not determine why the pilot had not dumped the full load or used a climbing flap.
A Sydney Seaplanes spokesman has said the company will make no further comments on technical matters while the investigation continues.
However, it is understood that the aircraft was entirely rebuilt, recertified and owned by several more businesses before it was acquired by Sydney Seaplanes.
The Civil Aviation and Safety Authority confirmed the plane had been repaired according to industry requirements before it flew again.
Sydney Seaplanes managing director Aaron Shaw said on Monday that the company took aircraft out of the water to check them every 100 flying hours.
He said engines were replaced every 1100 flying hours, 100 hours sooner than the industry standard, and the engine in the plane that crashed had only done 200 hours.
Property developer Denis O'Neil, who owned the plane in the early 2000s, said he had found it perfectly reliable as he flew between Sydney and the central coast.
"They're the safest planes in the world," he said. "I just feel for that family so much."
Ms Bowden and Mr Cousins, the head of the world's largest catering company, Compass, had sent out wedding invitations before coming to Australia for a holiday.
Ms Bowden's father, former British MP Gerry Bowden, said in a statement that the family was "devastated by the loss of dear Emma and dear Heather who spread happiness and joy among all they met throughout their lives".
Kevin Bowe, vice-president of the Seaplanes Pilots Association Australia, said his tourism company had operated several former crop dusters as seaplanes in the Whitsundays and any crashed plane would have been "completely overhauled" before returning to the air.
"They would be good as new, sometimes - quite often - better than new," he said.
Mr Bowe suggested a downdraft coming off the hill near Cowan Creek at Jerusalem Bay might have caused the aircraft to stall.
Investigators from the Australian Transport Safety Bureau aim to have recovered the largely intact aircraft from the water by the end of the week, using airbags or a crane, or both.
Nat Nagy, an executive director at the bureau, said he knew of no "systemic issues" with the DHC-2 plane model, which he considered reliable.
Another DHC-2 crashed in Canada in 2015, killing six, which prompted the Canadian Transportation Safety Board to recommend in September the mandatory installation of stall warning systems.
Only four of the 223 commercially operated models in Canada used such a system at the time of the recommendation and it is unclear whether the Sydney Seaplanes aircraft had one installed.