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.

Following the Air India Flight 171 crash, the FAA and Boeing have privately affirmed the safety of fuel switch locks on Boeing aircraft. India's AAIB preliminary report questioned if the fuel switches were accidentally activated,