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

Authorities released a preliminary report on the Air India crash, following an investigation. The London-bound flight from Ahmedabad crashed minutes into the June 12 flight. Only one passenger of the 242 passengers and flight crew survived.

A preliminary report into the Air India Flight 171 crash that killed 260 people, including 241 people on board, has been released. The London-bound aircraft, a Boeing 787-8 Dreamliner, crashed soon after taking off from the western Indian city of Ahmedabad on 12 June.