THE FLIGHT (Malaysian time is eight hours ahead of UK time).
What we do know:
Malaysia Airlines flight MH370, with 239 people on board, took off from Kuala Lumpur at 12:41am (local time) on Saturday March 8 heading north to Beijing.
At 1.07am, the plane sent its last ACARS transmission which provides engine maintenance data to the ground.
The ACARS (Aircraft Communications Addressing and Reporting System) was then deliberately switched off by someone on the jet.
The last words from the Boeing 777 were heard from the cockpit, where a person, believed to be the co-pilot, said: "All right, good night" to Malaysian air traffic control at 1.19am.
At 1.21am the jet, carrying 227 passengers and 12 crew, dropped off air traffic control screens after its transponder - which responds to civilian radar - was switched off on purpose by someone on board.
The plane which was north of Malaysia and flying towards Thailand was then deliberately diverted from its planned route as it is turned sharply to the west.
The plane, with 239 people on board, disappeared on March 8 At 2.15am, the flight was picked up by Malaysian military radar south of Phuket island in the Strait of Malacca, hundreds of miles west of its last known location.
At 8.11am - nearly seven hours after the plane was first thought to have gone missing - a satellite high above the Indian Ocean received the last signal from the aircraft.
The final "handshake" communication put the jet somewhere in one of two flight corridors.
One is a northern arc stretching from northern Thailand to Kazakhstan, the other is a southern one from Indonesia to the vast southern Indian Ocean.
The jet turned west as it was deliberately diverted from its planned route What we do not know:
Who deliberately switched off the plane's two crucial communication systems - ACARS and the transponder?
Was the co-pilot under duress when he made the last verbal contact with air traffic control?
Where exactly was the plane when it sent its last signal at 8.11am?
Did the plane crash or did it land safely? A Malaysian official has said the aircraft could have been on the ground when it sent its final signal.
Many countries are helping in the search for the jet THE SEARCH
What we know:
Some 26 countries are now looking for flight MH370, using at least 43 ships and 58 aircraft.
The nations helping in the hunt are Malaysia, Australia, Bangladesh, Brunei, China, France, India, Indonesia, Japan, Kazakhstan, Kyrgyzstan, Laos, Myanmar, New Zealand, Pakistan, Philippines, Russia, Singapore, South Korea, Thailand, Turkmenistan, UAE, UK, US, Uzbekistan and Vietnam.
Search teams are concentrating on the northern and southern flight corridors.
It is a massive area of millions of square miles, said to cover almost 10% of the entire planet.
The northern search corridor includes countries with busy airspace that likely would have noticed an unidentified aircraft in their territory.
China, India and Pakistan are among the nations that say they have seen no sign of the plane.
Australia is leading the search efforts in the southern Indian Ocean.
It has sent two AP-3C Orion aircraft, one of which is searching north and west of the Cocos Islands. Two more search aircraft will be deployed by Tuesday.
The search area has dramatically expanded. It was previously in the South China Sea and around India's Andaman and Nicobar Islands but these operations have now been halted or suspended.
People leave messages for the missing passengers What we do not know:
There has been speculation that the plane could have flown as low as 5,000ft using "terrain masking" to try to avoid radar.
Malaysian authorities have rejected these claims.
Of course, the main issue is that the exact location of the jet is still unknown.
THE SUSPICIONS
The investigation is focusing on the possibility the jet was deliberately diverted by the pilots or someone on board with considerable flying experience.
Police seized a flight simulator from the captain Zaharie Ahmad Shah's home on Saturday and also searched the co-pilot Fariq Abdul Hamid's home.
Authorities have said there were no suicide notes found at the properties.
Mr Zaharie, 57, was an active supporter of Malaysia's opposition, whose leader Anwar Ibrahim was convicted of sodomy - illegal in Muslim Malaysia - just hours before MH370 took off.
But those who knew Mr Zaharie rejected media reports he was deeply upset by the Anwar case.
Captain Zaharie Ahmad Shah (r) and co-pilot Fariq Abdul Hamid Mr Fariq, 27, had his reputation called into question by a South African woman who accused him of inviting her to join him in the cockpit for a journey in 2011, in breach of security rules.
Malaysia Airlines said it was "shocked" by the reported security violation, but could not verify the claims.
Investigators are checking backgrounds of all 227 passengers and 12 crew members, as well as the ground crew, to see if links to terrorists, personal problems or psychological issues could be factors.
Authorities are considering if the two pilots were involved in the disappearance, were they working together or alone, or with one or more of the passengers or crew?
Did they fly the plane under duress or of their own will?
Did one or more of the passengers manage to break into the cockpit or use the threat of violence to gain entry and then seize the plane?
And what possible motive could there be for diverting the jet?
Officials have not commented on reports that police were investigating a passenger who had aviation experience.
Mohd Khairul Amri Selamat said on social media sites he was a flight engineer working for a Swiss-based private jet charter company.
The 29-year-old's apparent experience means he would have a knowledge of in-flight computer systems and be able to carry out repairs.
And all the time the plane is not found, the anguish for the passengers' families goes on.
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