A year after the AI171 disaster claimed 260 lives, the cause of the crash remains unknown
Investigators say the inquiry is nearing completion, but key findings are yet to be released
The preliminary report found both engine fuel-control switches moved to cutoff moments after takeoff
A brief cockpit exchange raised questions, but unidentified voices left room for speculation
Human error, mechanical faults and software issues have all been suggested, without conclusive proof
An early final report can end speculation, aid safety reforms and provide closure to families