The model of seaplane that crashed and killed six people on New Year's Eve is generally reliable, according to a transport safety official leading the investigation.
But investigators do not know if the plane had the stall warning system recommended by Canadian authorities after the same model crashed and killed another British family in 2015.
The Sydney Seaplanes aircraft plunged into Jerusalem Bay north of Sydney, killing British chief executive Richard Cousins, 58, his sons Edward, 23, and William, 25, his fiance Emma Bowden, 48, her daughter Heather, 11, and pilot Gareth Morgan, 44.
The plane remains largely intact beneath 13 metres of water.
"The aircraft took off in a north-easterly direction, followed by a turn to the north-east, then a subsequent right hand turn prior to impact," Nat Nagy, an executive director of the Australian Transport Safety Bureau, said.
The 1964 aircraft then sank and settled on the bottom of the river in an "inverted, slightly nosedown altitude", Mr Nagy continued. He could not confirm that the plane nose-dived before hitting the water.
Authorities hoped to have recovered the plane by the end of the week. They may attempt to float it to the surface with internal airbags, pull it up with a crane, or both.
Three investigators from the ATSB are working to piece together the plane's brief, final flight, looking at factors from pilot history to maintenance to components.
In 2015, a plane of the same kind, a DHC-2 Beaver, crashed in Quebec, Canada, killing six on board. The Canadian Transport Safety Bureau recommended in September that all such planes be fitted with mandatory stall warning systems.
Mr Nagy said he did not know if the Sydney Seaplanes aircraft had this system but "we haven't seen any systemic issues with this aircraft".
Asked whether the model was reliable, he said "an aircraft that's been used this long in this many operations, I would say yes".
The safety bureau is appealing for witnesses to come forward, especially those who have video footage of the flight.
Investigators will try to recover any footage taken on the flight from mobile phones or body-cameras, before finishing a preliminary report within a month.