An Australian bouncy castle operator at the centre of a tragedy in 2021 that killed six children and seriously injured three has been cleared of breaching safety laws.

A court found Rosemary Anne Gamble, who runs the business Taz-Zorb, not guilty, ruling that the incident was "due to an unprecedented weather system" that was "impossible to predict".

The victims, who were on a bouncy castle at a primary school fun day in Devonport, Tasmania, fell about 10m (33ft) after strong winds blew the castle skywards at a school fair.

The verdict on Friday caused anguish among their families, with some crying out in court in disbelief, ABC News reported.

Prosecutors had accused Ms Gamble of failing to anchor the castle adequately, but her defence argued she could not have done more to eliminate or reduce hazards that led to the tragedy.

Magistrate Robert Webster agreed with the defence and found that the incident happened due to a dust devil - an upward spiralling vortex of air and debris - that was "unforeseen and unforeseeable".

"Ms Gamble could have done more or taken further steps, however, given the effects of the unforeseen and unforeseeable dust devil, had she done so, that would sadly have made no difference to the ultimate outcome," the magistrate said.

The six children killed in the accident - Addison Stewart, Zane Mellor, Jye Sheehan, Jalailah Jayne-Maree Jones, Peter Dodt and Chace Harrison - were aged between 11 and 12.

They were all at a Hillcrest Primary School fair when the accident took place on the last day of term before the school holidays in December 2021.

Five of the children were on the castle when the gales swept it up and flung it across the school oval.

The sixth child, who was waiting in line, died after being struck in the head by the inflatable blower.

The tragic accident shattered Devonport, a city on the north coast of Tasmania with some 30,000 residents.

Ms Gamble was charged nearly two years after, in November 2023.

Andrew Dodt, the father of one of the young victims Peter, said after Friday's verdict that "our hopes are just shattered now".

"At the end of the day all I wanted was an apology for my son not coming home, and I'm never going to get it, and that kills me," he said in a statement to local media.

"I've been broken for a long time, and I think I'm going to be broken for a lot more."

Ms Gamble's lawyer Bethan Frake spoke on her behalf, acknowledging that the incident has caused "scars that will remain for an extremely long time, likely forever".

"I am a mother," she said, quoting Ms Gamble. "I can only imagine the pain that other parents are living with each and every day because of this terrible thing that happened."

"Their loss is something I will carry with me for the rest of my life."