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.

Since the Tata takeover, India’s Directorate General of Civil Aviation has repeatedly fined Air India over safety and other regulatory violations, including an Rs8mn ($95,000) penalty last year for exceeding flight duty time limits. At home, it is competing in a near-duopoly with IndiGo, which has been boosting its international long-haul routes.