The families of the five men, including four US tourists, killed in a fiery Melbourne plane crash have few legal options for compensation, says an aviation lawyer.
Victorian pilot Max Quartermain was flying four Americans to King Island to play golf when his small plane crashed and exploded into a shopping centre moments after takeoff from Essendon Airport last month, accroding to news.com.au.
The Australian Transport Safety Bureau's preliminary report released on Wednesday ruled out an early theory of catastrophic engine failure during takeoff and is still trying to work out what caused the crash.
"Frustratingly for family members and the investigators, due to the substantial damage that the wreckage of the aircraft suffered, there is still no definitive cause or causes," Shine Lawyers aviation law principal Thomas Janson says.
Because a specific cause has not yet been found, families are restricted in any legal action they may want to pursue, Mr Janson says.
He said compensation could be sought for the nervous shock of the crash and dependency if relatives were financially reliant on the men killed.
Texan retirees Greg De Haven, Russell Munsch, Glenn Garland and John Washburn died on impact with Mr Quartermain when the plane hit the DFO.
They had been in Australia on a golfing "trip of a lifetime" with their wives, who were not on the flight.
• Essendon crash pilot's seven 'mayday' calls
According to the report, Mr Quartermain made seven mayday calls before his Beechcraft King Air crashed but anything else uttered in the last moments on-board remains a mystery because the black box failed.
All the recovered audio was from a previous flight on January 3, 2017.
Investigators will now look at the propellers to determine the blade angles at impact, their pre-impact condition and to assess the impact damage.
The ATSB will release a final report in about 12 months.