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

Investigators are probing the wreckage and cockpit recorders to understand what went wrong just after take-off. The Air India flight climbed to 625 feet in clear weather before losing location data 50 seconds in, per Flightradar24. Saturday's 15-page report offers early insights.

A focus on the Boeing 787’s fuel switches in a preliminary assessment raised questions about the pilots’ actions, but much is still unknown about Flight 171.