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

Preliminary findings into last month’s Air India plane crash suggest the aircraft’s fuel control switches were turned off, causing a loss of engine thrust shortly after takeoff.

Investigators probing a deadly Air India crash said in a preliminary report that the aircraft's engine fuel switches were flipped to an off position briefly, leading to confusion in the cockpit and putting focus on the pilots flying the Boeing 787.