Former Australian prime minister Tony Abbott has claimed "very top" level Malaysian officials believed vanished Flight MH370 was deliberately downed by the captain in a mass murder-suicide. No sign of the plane was found in a 120,000-square kilometre (46,000-square mile) Indian Ocean search zone and the Australian-led search, the largest in aviation history, was suspended in January 2017. The disappearance of the plane has long been the subject of a host of theories -- ranging from the credible to outlandish -- including that veteran pilot Zaharie Ahmad Shah had gone rogue.