The hunt for missing flight MH370 has expanded to involve 25 countries searching across swathes of ocean and much of Asia, in what has become the biggest ever search for a missing aircraft.

Concerns over the role of the pilot intensified after it emerged that a message was radioed to air traffic control even after the first set of aircraft communications had been switched off. Giving no sign of any trouble, the pilot’s last words to Malaysian air traffic control were “all right, good night”.

The sheer size of the search for the missing aircraft is likely to pose challenges for the sharing of sensitive military data, diplomats said. Hishamuddin Hussein, Malaysia’s defence and acting transport minister, said the move could bring “new challenges of co-ordination and diplomacy to the search effort”.