According to Malaysian officials, the co-pilot of missing flight MH370 spoke the last words to ground controllers before it vanished.
Investigators are looking into the possibility that Malaysia Airlines jet’s crew were involved in its disappearance.
The search for the plane has extended into two vast air corridors.
Twenty-six countries have been asked to help find the jet, which went missing over a week ago with 239 people on board.
Malaysia says the plane was intentionally diverted and could have flown on either a northern or southern arc from its last known position.
Ahmad Jauhari Yahy, chief executive of Malaysia Airlines, told a press conference on Monday that initial investigations had indicated that co-pilot Fariq Abdul Hamid had calmly said: “All right, good night” shortly before the plane disappeared.
However, it is not clear whether the last words came before or after one of the plane’s tracking devices was switched off. Officials believe the communications systems were deliberately disabled.
Police have searched the homes of Captain Zaharie Ahmad Shah, 53, and Fariq Abdul Hamid, 27.
A flight simulator taken from Zaharie Ahmad Shah’s home was being reassembled and examined at police headquarters, officials said.
Investigators are also looking at passengers, engineers and other ground staff who may have had contact with the aircraft before take-off.
The plane left Kuala Lumpur for Beijing at 00:40 local time on March 8.
Officials say the sign-off to air traffic controllers came at 01:19 as it left Malaysian airspace.
The last transmission from the plane’s Aircraft and Communications Addressing and Reporting System (ACARS) was received at 01:07.
“We don’t know when the ACARS was switched off after that,” Ahmad Jauhari Yahy said.
“It was supposed to transmit 30 minutes from there, but that transmission did not come through.”
The plane disappeared off air traffic controllers’ screens at 01:21, when it was over the South China Sea.
Searches have started in two air corridors – one stretching from the border of Kazakhstan and Turkmenistan to northern Thailand, and another from Indonesia to the Indian Ocean.
Two-thirds of flight MH370 passengers were from China and the country’s state media has been criticizing the Malaysian operation.
Chinese PM Li Keqiang in a phone call asked the Malaysian PM Najib Razak to provide more detailed information about the missing flight “in a timely, accurate and comprehensive manner”, state news agency Xinhua reported on Monday.
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