Authorities in India have released the preliminary results of their investigation into the the Boeing 787-8 Dreamliner crash in June that killed 229 of the 230 passengers aboard and all 12 crew members.

An official report on the world’s deadliest aviation accident in a decade, seen by CNN, has answered one key question – but raised others.

Boeing investors finally have details from a preliminary accident report for Air India flight 171, which crashed on June 12 less than a minute after taking off from an airport in Ahmedabad, India.