An appetite for risk might have influenced the pilot involved in a fatal helicopter crash in Broome three years ago.
The Robinson R44 broke up in mid-air and plummeted to the ground on July 4, 2020, killing local pilot and tourism operator Troy Thomas and 12-year-old Amber Jess Millar, and seriously injuring two others.
In its final report into the crash, the Australian Transport Safety Bureau said on Wednesday the pilot's "high-risk appetite" may have contributed to his decision to fly despite failing to identify the source of unusual mechanical vibrations.
The findings suggested Mr Thomas had a history of deliberately taking risks such as flying with too many passengers and flying low without required qualifications.
The report also revealed he was not legally allowed to fly, as he did not hold a valid aviation medical certificate.
"The findings are beyond disturbing and it confirms Amber's death was totally preventable on numerous levels, which highlight a complete disregard for aviation safety," Amber Millar's father Clint Benbow told ABC Radio.
Waiting for answers over the almost three years since the tragedy had been excruciating, he said.
"It's been the most drawn-out, painful, soul-destroying experience because obviously being classified you can't talk about the detail that's been gathered through the investigation."
Pilots had previously reported vibrations in the helicopter's tail rotor pedals.
The ATSB report found an overstress fracture caused the tail rotor gearbox to separate from the body of the chopper shortly after takeoff.
However no one officially reported the issue via a maintenance release form, which meant the aircraft could still be used.
Mr Benbow slammed the failure, saying it could have prevented deaths.
"If the maintenance document had been used, regardless of what was said verbally, it would have taken someone's authorised signature to bring that helicopter back into service," he said.
"And that form was not used at all."
A mechanical inspection the day before the accident didn't disclose the defects.
ATSB chief commissioner Angus Mitchell said the next step should have been to conduct a graduated flight check with the chopper hovering. Instead, it was used for a high-power take-off for the scenic flight with three passengers aboard.
The pilot should have heeded warnings that unusual vibrations could indicate a critical part had failed, he said.
"The pilot's handbook states that pilots should land as soon as possible and formally declare the helicopter unserviceable."
Mr Mitchell added the helicopter should not have been returned to service until the source of the vibration had been found and rectified.
The industrial estate where it launched from was also not an approved site.
Amber's mother, Fiona Benbow, watched the aircraft take off and then come crashing down again moments later.
"It was like a gunshot going off in my ears and I turned around instantly to see the helicopter spiralling out of control, coming down heavily on Amber's side," she told the ABC.
"I could see her face as it tumbled twice, a full circle, and then it hit the ground really, really hard."
She and several bystanders desperately tried to save Amber's life and help the other passengers - Mr Thomas' daughter Mia and family friend Maddison Down from Mandurah - but her injuries were too severe.
The Benbows have called for a Worksafe investigation and better regulation on aviation tourism in the hope their daughter's legacy will promote safety and change.
"All we are left with is the silence in our home which is deafening, the emptiness, the hollow echo that burns a whole right through us," they said in a statement also released on Wednesday
"No more sounds of laughter from you and your beautiful friends having fun, enjoying yourselves ... Nothing but sadness and broken hearts."
