Investigators have found a voice recorder that may have captured the final words of three Americans killed when their firefighting plane crashed in southern NSW.
The large aerial water tanker was swallowed by flames after crashing in the Snowy Mountains region while battling bushfires on Thursday afternoon.
Captain Ian McBeth, first officer Paul Clyde Hudson and flight engineer Rick DeMorgan Jr were killed.
Australian Transport Safety Bureau boss Greg Hood said investigators found the cockpit voice recorder while searching the plane's charred wreckage on Saturday.
It was not clear whether the recording would shed light on the cause of the crash, he noted.
"The cockpit voice recorder might be very useful, or it might not be. It depends on what was said," he told reporters near the crash site on Saturday.
"It generally records the last two hours of a flight. We should have some indication tomorrow when the data is downloaded."
Investigators began searching the crash site at first light on Saturday.
"Tomorrow we will bring in the 3D mapping drone," Mr Hood said.
"We will also go into town in Cooma and start taking witness statements from (Rural Fire Service) personnel that observed the accident sequence."
A relative of one of the men arrived in Sydney on Saturday, accompanied by representatives of Coulson Aviation, the Canadian company that operated the C-130 Hercules.
Relatives will be offered the chance to visit the crash site next week.
The men's bodies were recovered by police on Friday.
Images of the crash site were released by NSW Police.
Only the tail of the plane remains upright, surrounded by fractured debris and scorched trees.
Coulson has described the three airmen as "fallen heroes" and said their deaths would be "deeply felt by all" in the aviation industry and emergency service sector.
Florida father-of-two Mr DeMorgan, 43, spent 18 years in the US Air Force as a flight engineer on C-130s with extensive combat experience.
His loss was "surreal", his sister said online.
"He was a beloved friend, colleague, father, son and most of all, brother," Jen DeMorgan posted online.
"To most the sky was the limit, to them it was home."
Coulson Aviation said Capt McBeth's love for his wife Bowdie and three children "was evident for anyone who spent time around him".
Flags will fly at half-mast on Saturday in Montana, where the highly-qualified 44-year-old pilot flew with the National Guard.
Mr Hudson, a 42-year-old from the outskirts of Phoenix, spent 20 years as a US Marine, flying C-130s and receiving many decorations as he reached the rank of lieutenant colonel. He is survived by his wife Noreen.
The men are among six firefighters and 25 people who have died in NSW's unprecedented bushfire season.