KUALA LUMPUR, March 17, 2014 (AFP) - An investigation into the pilots of missing Malaysia Airlines Flight 370 intensified Monday as officials confirmed that the last words spoken from the cockpit came after a key signalling system was manually disabled.
US intelligence efforts also were focusing on Captain Zaharie Ahmad Shah and his first officer, Fariq Abdul Hamid, according to a senior US lawmaker.
"I think from all the information I've been briefed on from, you know, high levels within homeland security, national counterterrorism centre, intelligence community, that something was going on with the pilot," said Michael McCaul, the chairman of the House Homeland Security Committee.
"I think this all leads towards the cockpit, with the pilot himself, and co-pilot," McCaul said on Fox News Sunday.
Malaysia's Transport Minister Hishammuddin Hussein confirmed that an apparently relaxed final voice communication from the cockpit - "All right, good night" - came after the Aircraft Communications Addressing and Reporting System (ACARS) had been deliberately shut down.
ACARS transmits to the ground key information on a plane's condition.
It has not been confirmed who gave that final voice message. But the assumption is the person would have known the ACARS system had been disabled.
The plane's transponder - which relays radar information on the plane's location - was switched off 14 minutes after ACARS went down.
Shortly afterwards the plane disappeared from civilian radar. It continued to show up as a blip on military radar, but was not immediately identified as the same flight.
The plane went missing early in the morning of March 8 with 239 passengers and crew aboard, spawning a massive international search across Southeast Asia and the Indian Ocean that has turned up no trace of wreckage.
Two-thirds of the passengers on board the flight were Chinese, and state media in China attacked Malaysia anew on Monday for its handling of the crisis.
"The contradictory and piecemeal information Malaysia Airlines and its government have provided has made search efforts difficult and the entire incident even more mysterious," the state-controlled China Daily newspaper wrote in an editorial.
For relatives of those on board, a hijacking scenario provides a slim hope that the plane might have landed undetected somewhere.
"If they found the wreckage of the plane then that would be finalised because there's no hope," said Australian David Lawton, whose brother was on the plane.
"But while you've got hope, you've got worries too. Because if they're alive, are they being treated well, or what's happening?" he told Fairfax media.
The number of countries involved in the physical search for the jet has nearly doubled over the past two days to 26, after satellite and military radar data projected two dauntingly large corridors the plane might have flown through.
The northern corridor stretches in an arc over south and central Asia, while the other swoops deep into the southern Indian Ocean towards Australia.
Malaysia announced that it was deploying its naval and air force assets to the southern corridor, with Australian Prime Minister Tony Abbott vowing substantial assistance.
Three officials from France's civil aviation accident investigation agency arrived in Kuala Lumpur on Monday to share their experiences of the search for Air France Flight 447, which crashed in the Atlantic Ocean in 2009.
The "black boxes" from that crash were eventually recovered nearly two years later from a depth of more than 3,800 meters (12,500 feet).
The Malaysian authorities have stressed that the backgrounds of all the passengers and crew are being checked - as well as engineers who may have worked on the plane before take-off.
Senior US intelligence officials cited by the New York Times said they had run the names of everyone on board through their data banks without any tangible result.
That included a check on a passenger identified as an artist belonging to China's Muslim Uighur minority. Uighur separatists have become increasingly militant in their fight against Chinese rule.
Malaysian police have searched both pilots' residences and are examining a flight simulator that Captain Zaharie, 53, had installed at his home.
Associates say Zaharie was an active supporter of Malaysia's political opposition headed by veteran politician Anwar Ibrahim.
In a highly controversial case, Anwar was convicted of sodomy - illegal in Muslim Malaysia - just hours before MH370 took off.
But friends say Zaharie exhibited no extreme views.
Fariq, meanwhile, was accused in an Australian television report of allowing two young South African women into the cockpit of a plane he piloted in 2011, breaching security rules imposed after the 9/11 attacks in the United States.
But acquaintances have attested to his good character, and reports said he planned to wed his flight-school sweetheart.
Hishammuddin noted that the two pilots "did not ask to fly together" on flight 370.