Air India's deadly plane crash that killed at least 270 people has triggered a wave of speculation about what led to the world's worst aviation disaster in a decade, but authorities are slowly narrowing down areas of investigation.

Indian investigators have recovered the digital flight data recorder or the black box of the Air India flight that crashed a day earlier.

As the investigation continued Friday into the horrific Air India Boeing 787 Dreamliner crash that killed at least 290 people, the sole survivor is doing well but is "psychologically disturbed."