A seaplane crash that killed a British family of five may have been caused by one of them accidentally knocking the pilot unconscious.
The claim was made by Jerry Schwartz, who has recently become a partner at Sydney Seaplanes.
He told The Australian newspaper: "The investigation has shown that safety is good and it's actually believed to not be pilot error.
"The current belief is the passenger at the front actually knocked out the pilot."
The newspaper reported the passenger may have accidentally struck the pilot in the head while moving his arm to take photos of the Hawkesbury River.
The group was on a New Year's Eve "fly dine" sightseeing trip to Rose Bay in Sydney Harbour last year when the de Havilland DHC-2 Beaver floatplane flew dramatically off course before diving into Jerusalem Bay, north of Sydney.
British businessman Richard Cousins, 58, his fiancee Emma Bowden, 48, her 11-year-old daughter Heather and Mr Cousins's sons William, 25, and Edward, 23, were all killed.
Mr Cousins had been due to step down from his position as chief executive of catering giant Compass a few months later, while his son Will was head of press for pro-European Union campaign group Open Britain.
Also killed was the plane's Canadian-born pilot Gareth Morgan, 44.
A preliminary report by the Australian Transport Safety Bureau found there were no mechanical defects in the plane, the pilot was well qualified and the plane's maintenance checks were up to date.
A full report is due next year and there is also likely to be an inquest in Australia.
The pilot's cause of death has not been released but earlier this year it was revealed that the passengers died from head injuries, drowning, or both.
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Sydney Seaplanes managing director Aaron Shaw has previously blamed the accident on pilot incapacitation, saying: "Something definitely happened to the pilot to incapacitate him".
Soon after the crash, he had said: "A turn of this nature at low altitude by a pilot with Gareth's skills, experience and intimate knowledge of the location is totally inexplicable."