Data recovered from a home flight simulator owned by the captain of Malaysia Airlines Flight 370 showed that someone used the device to plot a course to the southern Indian Ocean, where the missing jet is believed to have crashed, Australian officials have said.
Confusion has reigned over what was found on Captain Zaharie Ahmad Shah's flight simulator since New York Magazine reported last week that an FBI analysis showed he had conducted a simulated flight to the southern Indian Ocean less than a month before the plane vanished along a similar route.
Malaysia rejected the report as false, but Australia's Joint Agency Co-ordination Centre confirmed on Thursday that the captain's simulator did indeed show that "someone had plotted a course to the southern Indian Ocean".
The Boeing 777 vanished with 239 people on board after flying far off course during a flight from Kuala Lumpur, Malaysia, to Beijing, China, on March 8 2014.
New York Magazine cited the discovery as strong evidence that the disappearance was a premeditated act of mass murder-suicide at the hands of the captain.
But Malaysia's national police chief Khalid Abu Bakar said police had never handed any document or information to any authority abroad, including the FBI - a perplexing statement, given that Malaysia's own transport minister confirmed two years ago that Malaysia was working with the FBI to analyse data from the simulator's hard drives.
Adding to the confusion, the Joint Agency Co-ordination Centre, which is overseeing the search for the plane off Australia's west coast, subsequently issued a vague statement that seemed to imply such a route had been found on Capt Zaharie's machine.
The agency then warned that evidence of the route did not prove that he had planned to steer the plane off course and showed only "the possibility of planning" for such an event.
Pressed for clarification, the agency confirmed in an email to The Associated Press news agency on Thursday that the captain's simulator did show that "someone had plotted a course to the southern Indian Ocean".
The confirmation appears to directly contradict repeated assertions from Malaysian officials that no such route had been found on the captain's simulator. On Wednesday transport minister Liow Tiong Lai insisted there was no evidence to prove that Capt Zaharie had plotted the same course as the doomed airliner into the machine.
Earlier this week Australian prime minister Malcolm Turnbull declined to offer any details on what evidence had been found on the simulator, saying it was a matter for Malaysia, which is leading the investigation into the missing plane.
"I just note that even if the simulator information does show that it is possible or very likely that the captain planned this shocking event, it does not tell us the location of the aircraft," Mr Turnbull told reporters.
Officials have been stumped in their efforts to explain why the plane veered so far off course. Theories have ranged from a deliberate murder-suicide plot by one of the pilots to a hijacking and a mechanical catastrophe.
Similarly, search crews have been unable to find the main wreckage of the plane despite a sweeping underwater hunt of a remote stretch of ocean off Australia's west coast.
Last week officials from Malaysia, Australia and China announced that the underwater search would be suspended once the current search area had been completely scoured.
Crews have fewer than 3,900 square miles left to scan of the 46,300-square-mile search area and should finish their sweep of the region by the end of the year.