Australian investigators have defended their search for Malaysian Airlines flight 370, saying it was unlikely the pilot performed a controlled ditching.
Australian Transport Safety Bureau's Greg Hood and Peter Foley told a Senate estimates hearing on Tuesday they deeply regretted not being able to find the plane and the 239 people on board.
Mr Foley said claims the ATSB had ignored a theory in which the pilot flew the plane to the end were wrong.
A recent book by Canadian Larry Vance, a former commercial pilot who worked as a senior air-crash investigator with Canada's Transportation Safety Board, cast doubt on the ATSB's findings.
Mr Vance presents evidence contradicting the bureau's conclusion MH370 likely entered an out-of-control high-speed descent and crashed into the ocean.
But Mr Foley told the hearing the last transmission from the plane was incomplete and probably triggered by fuel exhaustion.
"There's no earthly reason why someone in control of an aircraft would exhaust its fuel and then attempt to glide it when they have the option of ditching," Mr Foley said.
"The aircraft was probably descending in an uncontrolled manner."
One of the plane's flaps found off the coast of Tanzania in July 2015 was a crucial piece of evidence, Mr Foley said.
He said that showed the flaps weren't deployed at the end of the flight, meaning the aircraft was uncontrolled or poorly controlled.
"We have quite a lot of evidence to support no control at the end," he said.
Mr Foley also dismissed suggestions the pilot had depressurised the cabin to incapacitate passengers.
He said that theory relied on the pilot fighting the effects of decompression sickness for an hour, which was unlikely given the pilot was 53 and overweight.
The hearing also was told Australia contributed $63 million to the search for MH370.