Kuala Lumpur: The final words from the cockpit of a missing Malaysian jetliner gave no clue of anything wrong even though one of the plane's communications systems was disabled, officials say.
The finding, they say, adds to suspicions one or both of the pilots were involved in the disappearance.
As authorities examine a flight simulator confiscated from the home of one of the pilots and dig through the background of all 239 people on board and the ground crew that serviced the plane, they are also grappling with the enormity of the search ahead, warning that they need more data to narrow the hunt.
The Malaysia Airlines Boeing 777 took off from Kuala Lumpur about 12.40am on March 8, headed to Beijing.
On Saturday, Malaysia's government confirmed the plane was deliberately diverted and may have flown as far north as Central Asia, or south into the vast reaches of the Indian Ocean.
Authorities have said someone on board the plane first disabled one of its communications systems - the Aircraft and Communications Addressing and Reporting System or ACARS - at 1.07am.
About 14 minutes later, the transponder, which identifies the plane to commercial radar systems, was also shut down.
The fact they went dark separately is strong evidence the plane's disappearance was deliberate.
On Sunday, Malaysian Defence Minister Hishammuddin Hussein said the final words from the cockpit - "All right, good night" - were spoken to air traffic controllers after the ACARS system went off.
Whoever spoke did not mention any trouble on board, seemingly misleading ground control.
Air force Major General Affendi Buang told reporters he did not know whether it was the voice of the pilot or co-pilot.
Given the expanse of land and water that might need to be searched, the wreckage of the plane might take months - or longer - to find, or might never be located.
Establishing what happened with any degree of certainty will likely need key information, including cockpit voice recordings, from the plane's flight data recorders.
The search area now includes 11 countries the plane might have flown over, Mr Hishammuddin said, adding that the number of countries involved in the operation had increased from 14 to 25.
Mr Hishammuddin said he had also asked governments to hand over sensitive radar and satellite data to try and help get a better idea of the plane's final movements.
Malaysia's police chief, Khalid Abu Bakar, said he requested countries with citizens on board the plane to investigate their background, no doubt looking for any ties to terrorist groups, aviation skills or evidence of prior contact with the pilots.
He said the intelligence agencies of some countries had already done this and found nothing suspicious, but that he was waiting for others to respond.
The government said police searched the homes of both pilots on Saturday, the first time they had done so since the plane went missing.
Mr Khalid said officers confiscated the elaborate flight simulator that one of the pilots, Zaharie Ahmad Shah, had built in his home and reassembled it to study it for clues.
Malaysian officials and aviation experts said whoever disabled the plane's communication systems and then flew the jet must have had a high degree of technical knowledge and flying experience.
AP via SMH.COM.AU