Investigators, led by India’s Aircraft Accident Investigation Bureau with the assistance of the NTSB, have been piecing together evidence to determine what caused Air India Flight 171 to crash on June 12,

The left engine separated from the aircraft and struck the north corner of this building at ground level. The aircraft's right engine was found resting beneath a concrete water tank on the building's rooftop. The inboard section of the right wing was recovered near this area.

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