A seaplane that crashed near Sydney killing five Britons had taken a "totally inexplicable" turn, the aircraft's operator has said.

An official report into the crash found the aircraft was "away from the expected and standard flight path" before it nose-dived into Jerusalem Bay on New Year's Eve.

British businessman Richard Cousins, his sons Will and Edward, Mr Cousins' fiancee Emma Bowden and her 11-year-old daughter Heather were all killed, along with Australian pilot Gareth Morgan.

Investigators are trying to piece together what happened in the cockpit, and one line of inquiry will be if Mr Morgan was incapacitated, according to the Australian Transport Safety Bureau (ATSB).

There is no evidence to suggest the crash was deliberate, it added.


Several witnesses reported that the plane took a steep right turn before the aircraft collided with the water "in a near vertical position", the bureau's preliminary report found.

Image: (clockwise from top left) Richard Cousins, Ed Cousins, Emma and Heather Bowden, and Will Cousins.

The seaplane did not have a cockpit voice or flight data recorder but there are hopes mobiles phones recovered from the scene may shed light on events prior to the crash.

After the report's findings were published, Sydney Seaplanes boss Aaron Shaw said: "It is not a route we authorise in our landing and take-off area register and the plane simply should not have been where it was.

"Further, the aircraft is then reported to have entered in to an 80 to 90-degree bank angle turn.

"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."

Mr Morgan, who had more than 10,000 hours of flying experience and had flown seaplanes in the High Arctic and Maldives, was said to have a "high standard of health".

The ATSB said it had "no information at all" to suspect the crash had been deliberate and it had received no evidence to suggest concern about Mr Morgan's mental health.

Seaplane wreckage lifted on to barge

Investigators are also considering if any of the passengers may have suffered a medical episode that could have contributed to the crash.

The results of post mortem examinations and toxicology tests will be provided to the New South Wales coroner by the state's police.

The bodies of Mr Cousins, 58, his sons, Will and Edward, aged 25 and 23, Ms Bowden, 48, and her daughter were recovered from the water on the day of the tragedy.

Mr Cousins was due to step down from his position as chief executive of catering giant Compass in March, while his son Will was head of press for pro-European Union campaign group Open Britain.

The family had gone for lunch and taken the flight about 3pm to return to Rose Bay, near Sydney Harbour.