Kuala Lumpur: Two weeks into the search for missing Malaysia Airlines Flight 370, the fundamental questions of where? how? who? and why? remain unanswered, although some information has been uncovered that points in certain directions.
Here are some of the key questions and a look back at what has been learned over the past 14 days.
"The one thing everyone wants to know is the one thing we can't answer. Where the plane is." -- this phrase, with slight variations, has become something of a daily mantra for Malaysian Transport Minister Hishammuddin Hussein at his press briefings.
The whereabouts of the plane remain the most immediately perplexing issue, not least because many find it difficult to accept the idea that a plane as large and sophisticated as a Boeing-777 can just vanish in the modern technological era.
The initial search focused on the South China Sea which the plane had been crossing when it dropped off military radar.
Sketchy satellite and military radar data saw efforts switch to the opposite, Indian Ocean-side of the Malay peninsula where investigators used the data to identify two giant search corridors, running south into the Indian Ocean and north over South and Central Asia.
Most experts favoured the southern maritime corridor, querying how the plane could have flown undetected over the dozen or so countries in the northern corridor.
The Malaysian authorities insist that both corridors are still "equally important" but resources were flooded into a remote stretch of Indian Ocean 2,500 kilometres (1,500 miles) southwest of Perth, after Australia released grainy satellite images on Thursday that showed what could be floating pieces of wreckage in the area.
At the limit of the plane's range, the site location reinforced the belief that the plane may have flown on until it ran out of fuel.
The photos galvanised the search just as it was showing signs of flagging, but three days without any sign of debris has dampened the initial excitement.
WHAT HAPPENED?
Depending on the circumstances in which the plane is found -- if it is found -- determining what actually happened on board could take years.
Of the many initial scenarios, the only one that has been effectively ruled out is a mid-air explosion that immediately destroyed the aircraft.
Multiple scenarios exist, but three dominate: hijacking, pilot sabotage, and a mid-air crisis that incapacitated the flight crew and left the plane flying on auto-pilot until the fuel ran out.
"Up to this point, I don't see any consensus either within the intelligence community, the aviation community or among governments as to what really went on," said Jonathan Galaviz, a partner at US-based airline and travel consultancy Global Market Advisors.
The Malaysian authorities maintain that the plane's movement after it dropped off civilian radar, coupled with the disabling of its automated signalling systems, all point to "deliberate action" by someone on board.
If the plane did crash in a remote area of the Indian Ocean, the 'incapacitated' crew scenario will likely gain traction.
Many relatives of the passengers have pushed a hijacking scenario in which the plane was secretly landed somewhere. But no demands have been made and analysts have struggled to suggest who would hijack a Malaysian jet and why.
ANY SUSPECTS?
Background checks on the 227 passengers have come up empty, despite some initial concern over two men travelling on stolen EU passports.
The Malaysian authorities insist everyone remains under investigation, including ground crew who worked on the plane before departure, but the spotlight has undoubtedly been on the Malaysian captain and his co-pilot.
Police searched both pilots' residences and removed a flight simulator from the captain's home. Many pilots are known to use home simulators.
The final words from the cockpit -- "All right, good night" -- were believed to have been spoken by the co-pilot.
No evidence has yet emerged implicating either man.
WHAT NEXT?
The priority remains the search for the plane, with a special focus on locating the "black box" before it stops emitting locator signals after 30 days.
But locating the plane does not necessarily mean understanding what happened to it and Transport Minister Hishammuddin says Malaysia and its 25 search partners must prepare for the "long haul."
If it is found in the southern Indian Ocean, questions of investigative jurisdiction may arise in a case that has already tested the limits of regional cooperation.
"At this point, officials are probably quite aware that the winter season for the Southern Ocean is approaching," said Greg Waldron, Asia managing editor of Flightglobal magazine.
"That is going to make conditions more difficult, in what is already is a bad part of the world to be mounting a search effort."
