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

The granddaughter of a victim of the Air India Flight 171 crash has said a preliminary report into the incident was "incomplete" and that she "can't be at peace" without those responsible being held accountable.

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.