The preliminary finding gives investigators a new line of inquiry as they study a crash that killed all but one of the plane’s passengers.

Investigators in India are studying the black boxes of a Boeing 787 Dreamliner after recovering them from the aircraft wreckage to ascertain the cause of last week's plane crash that left at least 270 people dead.

India's aviation safety watchdog said on Tuesday surveillance conducted on Air India's Boeing 787 fleet did not reveal any major safety concerns, days after one of its jets crashed, killing at least 271 people.