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.

Management installed by the Tata Group had spent three years struggling to undo a reputation for shoddy operations earned during decades of state ownership.

News of the sole survivor of an Air India plane crash that killed the other 241 people aboard has led to endless fascination online.