Firefighters in Australia held a minute's silence on Friday for three US colleagues killed in a plane crash as investigators scoured the accident site in remote bushland.
Flags on official buildings in New South Wales (NSW) state, where the C-130 Hercules crashed while on a mission to dump retardant on a huge wildfire, were flown at half-mast as a mark of respect.
"We will forever be indebted to the enormous contribution and indeed the ultimate sacrifice that's been paid as a result of these extraordinary individuals doing a remarkable job," NSW Rural Fire Service Commissioner Shane Fitzsimmons said at a farewell near Sydney airport for 32 US firefighters who were returning home after weeks on duty on Australia.
Fitzsimmons and air safety officials said it was too early to speculate on the cause of the crash.
"We simply don't know the circumstances pertaining to the accident at this stage," Fitzsimmons said. "Appropriate, formal investigations and inquiries are underway."
The three crew who died were Ian McBeth, 44, Paul Hudson, 42, and Rick DeMorgan Jr., 43, their employer, Canadian firm Coulson Aviation said in a statement. All three had previously worked for the US military. Two were married and two left-behind children.
"We honour the amazing crews who do incredible things in dangerous circumstances supported by world-class operations," Coulson Aviation said in a statement.
The company had grounded its other large air tankers immediately after the crash on Thursday but said they would be returning to work "in the very near future".
Fitzsimmons earlier said field reports showed there had been a "pretty significant fireball associated with the plane crash", while a spokesman for Australia's Civil Aviation Safety Authority told Reuters the aircraft went into a valley to drop the retardant and did not emerge.
The Australian Transport Safety Bureau said it would provide a preliminary report in about 30 days, after analysing available recorded data, reviewing weather information and interviewing any witnesses.
The owner of the aircraft, Canadian aerial firefighting company Coulson Aviation, was sending a team to help with the investigation. They are due to arrive in Sydney on Saturday morning, Fitzsimmons said.
A US National Transportation Safety Board official said the agency plans to have some involvement and will likely send an investigator or two to Australia.
There have been two previous crashes involving C-130 Hercules aircraft while fighting wildfires. In a 2002 accident in California, caught on videotape, the wings of the aircraft folded upward, breaking off the plane before the fuselage rolled and hit the ground upside down, killing all three crew. In 2012, another C-130 crashed in South Dakota, killing four of the six crew, in an accident that was later determined to be weather-related.
"Unfortunately, aircraft are one of the riskiest parts of wildland firefighting," said Eric Kennedy, a disaster and emergency management expert at York University in Toronto, Canada.
Kennedy said there many possible causes for Thursday's crash but noted that a well-known risk in the C-130 fleet was metal fatigue-induced wing failure.
"Reduced visibility, high turbulence, and low flying can all be contributing risk factors for air tanker crashes," Kennedy said in emailed comments.
Australia's National Aerial Firefighting Centre, which leases planes on behalf of state governments for firefighting operations, said it currently has 165 aircraft on its books, including 10 large air tankers. When individual state plane ownership and contracts are taken into account, the pool of available aircraft grows to over 500, NAFC estimates.
SMOKE HAZE RETURNS
The plane crash on Thursday took the death toll for Australia's devastating bushfire season to 32, including eight firefighters. The wildfires have also killed millions of animals, razed thousands of homes and destroyed a land area about one-third the size of Germany since September.
Around 200 firefighters from the United States and Canada have undertaken deployments in Australia since the start of the season.
A 41-strong US team arrived in Melbourne from the United States on Friday to help in eastern Victoria, the state's Country Fire Authority said.
While fire conditions eased in southeastern Australia on Friday, Sydney was choking on a new smoke haze, blown in by a baking hot wind from the fires burning in the south of the state. The harbourside city was also covered in a layer of terracotta-coloured soil brought in from the west by huge dust storms.
In New South Wales, firefighters were tackling 95 blazes, but they were all at the lowest warning levels. In Victoria state, one out of 60 fires was rated at the warning level of "watch and act", meaning there was no immediate danger.