As the loved ones of the 227 passengers and 12 crew members aboard Malaysia Airlines Flight 370 try to come to terms with their deaths, one major mystery looms over the tragedy - why and how did the Beijing-bound jetliner end up in the southern Indian Ocean?
The Boeing-777's two black boxes could provide clues to solving the mystery of why the plane veered so far off course, but experts say that the search for them will be long and difficult.
In theory, the black boxes, with one containing flight data and the other cockpit voice recordings, will continue emitting tracking signals for about another two weeks, with an average audible range of 2-3km.
But since no plane debris has been confirmed in the vast and remote search area, finding the black boxes is like looking for a needle in a haystack.
Or as the Australia Defence Force vice-chief, Air Marshall Nick Binskin, puts it: "We're not searching for a needle in a haystack. We're still trying to define where the haystack is."
As the search for the missing plane, which was suspended on Tuesday due to bad weather conditions, is set to resume today, theories abound as to its fate.
The two more compelling theories:
This has gained most traction, with the possibility of the plane being either hijacked or taken over by a rogue pilot.
The fact that its data reporting system and its transponder - which reports its position in flight to ground-based radar - appeared to have been shut off at a 14-minute interval from one another suggests that they may have been deliberately disabled, US network ABC News reported.
The transponder was switched off soon after the final voice communication from the cockpit, around the same time that Malaysia believes the plane may have inexplicably started to turn back, the Washington Post said.
Taken together, this "suggests that someone unauthorised took control of that airplane, like an intruder or one of the pilots", the Post quoted one US flight crash expert as saying.
Britain's The Daily Telegraph, quoting well-placed sources, on Tuesday reported MH370 crashed into the Indian Ocean in an apparent suicide mission.
The team investigating the plane's disappearance believe no malfunction or fire was capable of causing its unusual flight or the disabling of its communications system before it veered wildly off course on a seven-hour silent flight into the sea, it said.
An official source told The Telegraph that investigators believe "this has been a deliberate act by someone on board who had to have had the detailed knowledge to do what was done... Nothing is emerging that points to motive."
Asked about the possibility of a plane malfunction or an onboard fire, the source said: "It just does not hinge together... (The investigators) point to it being flown in a rational way."
The investigation has focused on the pilot, Captain Zaharie Ahmad Shah. Much has been made of the 53-year-old pilot's homemade flight simulator.
The Malaysian police, with the help of the US Federal Bureau of Investigation, are trying to restore files deleted from the simulator last month to see if they shed any light on the tragedy.
Malaysian Acting Transport Minister Hishammuddin Hussein told a news conference last week that Mr Zaharie is considered innocent until proven guilty of any wrongdoing, and that his family was cooperating in the investigation.
Malaysia's Berita Harian, quoting an unnamed source, said that investigators had discovered the runways of five airports near the Indian Ocean loaded into Mr Zaharie's flight simulator.
"The simulation programmes are based on runways at the Male International Airport in Maldives, an airport owned by the US (Diego Garcia), and three other runways in India and Sri Lanka," the source said.
This theory by Mr Chris Goodfellow, a pilot with 20 years of experience, suggests that a fire on board the plane caused the pilots to set course for the nearest viable airport at Pulau Langkawi, which would correspond with the new route the jetliner appeared to have followed.
He first posted his "startlingly simple" theory on Google+ last Tuesday, and it was soon picked up by several publications, including Wired and Time magazines.
Once the course had changed, the fire could have melted electronic wire bundles, causing cyanide gas to be pumped through the cockpit and cabin, rendering everyone unconscious (oxygen masks do not help since cyanide gas can be absorbed through the skin), and leaving the plane heading along its path until it ran out of fuel, Time reported.
Mr Bruce Rodger, the president of the aviation consultancy Aero Consulting Experts, told the magazine: "It's my favourite analysis because it means there wasn't a bad guy doing something bad to an airliner."
The fire scenario could also explain the loss of communication systems, with either the pilots killing electrical busbars to contain the fire or an electrical fire causing the failure of various systems on board.
But there should still have been a distress call, Mr Greg Feith, a former National Transportation Safety Board crash investigator, told NBC News.
"Typically, with an electrical fire, you'll have smoke before you have fire. You can do some troubleshooting," he said.
Mr Michael G. Fortune, a retired pilot who flew Boeing 777s, said it was unlikely the crew would have shut off the transponders to deal with the fire.
"The checklist I utilised for smoke and fumes in the B-777-200ER does not specifically address the transponder being turned off," he said.
Mr Goodfellow's theory also does not explain how the plane had veered off its course towards Langkawi and headed south towards the Indian Ocean, if not for human intervention.
"Both the theory of foul play and that of a fire are possible and important to explore," concedes Mr Rodger. "But... I want to believe that the pilots did everything to save the airplane."
Get The New Paper for more stories.