Like US Airways, United is trying to secure a loan guarantee from the Air Transportation Stablisation Board (ATSB), but so far without success.

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The ATSB believe the plane became depressurised, leaving the pilot and passengers unconscious and the plane flying automatically until it ran out of fuel.

BBC: Australian 'ghost flight' still a mystery

"While an investigation report into a remote 440km per hour (270 mph) impact crash and subsequent fire which destroyed much of the evidence is always open to criticism, based on its initial reading of the 75 page report, the ATSB does not accept the coroner's criticisms, " it said in a statement.

BBC: Australian 'ghost flight' still a mystery