Three days after flight MH370 vanished mid-air as it flew 239 people from Malaysia to China, its whereabouts – and what happened – remains a mystery.
The Malaysia Airlines flight lost radio contact at about 5.30pm GMT, above the South China Sea somewhere between Malaysia and Vietnam.
False sightings of debris apparently from the aircraft have been quickly ruled out soon afterwards.
Channel 4 News asks – and attempts to answer – a few key questions about the flight.
Given so much of the sky is rigged up to numerous satellites, and with tracking technology as advanced as it is, the disappearance of anything as large as a Boeing 777 really is a mystery.
The plane, a Boeing 777-200 ER, was equipped with a transponder – an inbuilt tracker which automatically relays information about the flight (such as altitude) to ground radar stations. That stopped sending information.
Crews also have discrete radio channels, and most aircraft have at least one other back-up communication system. Nothing was sent through any of these channels either.
For all communication to suddenly stop, with a distress signal, would normally indicate some sort of sudden catastrophic failure.
The plane was comfortably cruising at a height of about 35,000 feet through the night sky above the South China Sea, so there should have been enough time for the pilot, Zaharie Ahmad Shah, 53, or the co-pilot, Fariq Abdul Hamid, 27, to send a distress signal. But they did not.
For all communication to suddenly stop, without a distress signal, would normally indicate some sort of sudden catastrophic failure which would not allow the crew time to send messages using the radio or through the transponder.
The Boeing-777 had an unblemished safety record in terms of fatalities from when it was launched, in June 1995, until 2013, when a botched landing in San Francisco killed two people.
The planes are kitted out with numerous back-up electrical systems, although the Air Accidents Investigation Branch has said that Boeing 777s were involved in at least a dozen incidents where electrical systems have overheated during or before flights.
The AAIB also said in December 2012 that there had been at least 15 occasions on which the engine thrust reverser was defective.
The US has reviewed imagery taken by American spy satellites for evidence of a mid-air explosion, but has not found anything to locate its whereabouts.
On the flight manifest, two passengers’ names have caught the eye of investigators: passenger number 63, Christian Kozel, apparently a 30-year-old Austrian national, and number 101, Luigi Maraldi, listed as a 37-year-old Italian national.
The Austrian and Italian governments said that neither of their men were on board the aircraft; Mr Kozel’s passport was stolen two years ago, and Mr Maraldi’s was stolen last year. On both occasions, the passports were stolen in Thailand.
The two passengers bought one-way tickets, and the airline KLM confirmed that two passengers of the same name were booked on subsequent flights that day: Mr Kozel was due to fly to Frankfurt, Germany, from Beijing, and Mr Maraldi was to fly on to Copenhagen, in Denmark.
But the two who used the stolen passports are far from alone. Interpol says it has a database of more than 40 million stolen or lost travel documents.
Interpol has chided authorities for failing to check the status of the two passports against its database. Last month, Ronald Noble, secretary general of Interpol, urged countries to screen passports against its database as otherwise “the result is a major gap in our security apparatus that is left vulnerable to exploitation by criminals and terrorists”.
Thailand is at the centre of a sophisticated and thriving trade in stolent and forged passports.
Comparisons have already been drawn between previous terrorist attacks and this disaster. Carl Ungerer, an independent security consultant and former adviser to Australian Foreign Minister Bob Carr, said the use of stolen passports resembles a 1994 attack on a Philippines flight by Ramzi Yousef, who used a stolen Italian passport.
But Thailand is at the centre of a sophisticated and thriving trade in stolen and forged passports, the majority of which are used for and by economic migrants seeking a life in a society where they can make more money.
People smugglers in south east Asia can charge tens of thousands of dollars to get people from the region into developed economies in the US or Europe, with many irregular migrants travelling through Bangkok first.
“I’m sure terrorists use forged documentation, but the vast majority of people who use forged documents are not terrorists,” said Professor Ronald Skeldon, Professorial Fellow in the Department of Geography at the University of Sussex.
The documents – passports and visas – would be used to gain access to countries that would otherwise be inaccessible, Professor Skeldon added.
The majority of forged or stolen documents are used to get migrants to Europe or the US, he said.
Business people, diplomats and academics familiar with the region say that it is common for flights in the region to have many seats occupied by irregular migrants.
No, they have not – which has led some to speculate that mechanical failure rather than terrorism may be behind the accident. After all, if the point of a terrorist attack is to gain exposure, the fact that no group can claim this one as theirs defeats that object.
There have been claims that Uighur separatists from China’s Zingjiang province may be likely culprits. They, however, have not said that they are, and counter-terror experts suggest that what has happened may be beyond such groups’ capabilities.
Clive Williams, a visiting professor at the ANU’s Centre for Military and Security Law, and an adjunct professor at Macquarie University’s Centre for Policing, Intelligence and Counter Terrorism, also suggested that other terrorist groups such as al-Qaeda or Chechen separatists have only targeted flights to the US or flights within Russia.
He does concede that the flight may have been bombed, but not necessarily for terrorist related reasons. “Back in 1972, my army boss was killed when Cathay Pacific Flight CX700Z was bombed between Singapore and Hong Kong, crashing in Vietnam… a Thai police officer was accused of planting the bomb in his wife’s luggage, intending to collect the insurance on her, but he was acquitted due to lack of evidence,” he wrote in the Sydney Morning Herald today.
For the families involved, every minute is like an hour. Please keep them in your thoughts as we continue to search for MH370 thru the night
— Malaysia Airlines (@MAS) March 10, 2014
What we can say is that if the plane has not crashed, it will certainly have run out of fuel by now.
Yet despite dozens of vessels and aircraft from 11 countries scouring the seas for wreckage, efforts have been without success.
Before the latest accident, the Air France flight 447 was the last passenger jet to vanish. En route from Paris to Rio de Janeiro on June 1, 2009, it hit a heavy thunderstorm and plunged into the Atlantic Ocean, off the coast of Brazil.
All 228 passengers and crew members were killed. It took days for searchers to spot wreckage from the aircraft floating 600 miles from land. But it took more than two years to discover what happened and why as it was only 2011 before divers found the jet’s black boxes at the bottom of the sea.
Vietnam intensifies search for #MH370, object suspected to be inner door hasn’t been recovered pic.twitter.com/5akV9WqaSz
— Vu Trong Khanh (@TrongKhanhVu) March 10, 2014
The plot thickened after it emerged, according to reports, that passengers’ family members reported ringing victims’ mobile phones. The phones rang, but nobody answered, according to a joint statement signed by 19 families.
In each case, the families said, the phone would ring but the call would be hung up.
The sister of one of the Chinese passengers rang his phone live on TV twice on Sunday morning and heard it ringing. She said she called again later that afternoon and heard it ring once more.
In the absence of credible information, conspiracy theories abound, and this is no exception.
One theory doing the rounds is that terrorists bearing fake passports hijacked the aircraft and are now secretly stationed at an abandoned Vietnamese airport.
In the absence of credible information, conspiracy theories abound, and this is no exception.
The hijackers may, according to this theory, have landed the plane safely so they could later use it as a weapon of mass destruction with passengers and crew apparently being held as hostages.
The usual culprits – UFOs and abducting alien life forces – have also been floated around.
Either way, the families of some 239 people have been told they should prepare for the worst, and once the dust has settled, someone is going to have to answer some very serious questions about safety and security.
China, which had the greatest number of nationals on board the plane, is likely to be have greatest grievance.
As the country’s Global Times wrote in an editorial: “If [the disappearance] is due to a deadly mechanical breakdown or pilot error, then Malaysia Airlines should take the blame. If this is a terrorist attack, then the security check at the Kuala Lumpur airport and on the flight is questionable.”