How did flight MH370 end up in the Indian Ocean? Eight questions that still need answers
The families of the 239 passengers have been left devastated - but will they ever know the truth about what happened?
Almost three weeks after it seemingly disappeared without a trace, there have now been four satellite sightings of objects in the Indian Ocean that could be linked to missing Malaysia Airlines flight MH370.
Using the technology from UK firm Inmarsat, it has been concluded the plane crashed somewhere in the southern Indian Ocean, west of Perth in Australia, with Australian, Chinese and French satellites all spotting objects within a broad search area.
Then today, it was announced that a possible "debris field", measuring 400 square kilometres and containing 122 objects, had been seen close to the others.
Malaysia's transport minister described the discovery as "the most credible lead we have" and, if proved to be linked to MH370, could finally bring closure for the families of the 227 passengers and 12 crew desperately waiting for news of their loved ones.
Follow live updates on the search here.
Their devastation will no doubt be immeasurable.
But what might make it harder, is that this conclusion doesn't bring us any closer to finding out what happened to cause the crash.
How did a passenger jet disappear from all communication channels and fly thousands of miles off course before crashing into a remote part of the ocean without anyone realising?
Here we look at the 8 key questions that still need to be answered:
1. Where did the plane crash?
Often investigators know where a plane crashed, even if they cannot immediately find debris.
It may take several years before the key parts of the plane is discovered - including the crucial black box.
Calculations from UK firm Inmarsat have pinpointed the last-known location of the plane to an area of the southern Indian Ocean, but that does not give us the crash site.
Added to that is the fact the sea around those parts is up to 23,000ft deep and currents are likely to have caused wreckage to drift a long way from the original crash site in the past two weeks.
The objects discovered so far are spread across hundreds of kilometres, meaning that even if they are from MH370, we may not know exactly where it came down.
On the plus side, even one single piece of wreckage may be enough for investigators to determine whether the plane exploded or crashed, for example.
2. Will the black box ever be found?
The most important piece of evidence to find is flight MH370's black box.
The piece of equipment - which is in fact usually orange - is around 12 inches long and designed to survive virtually any impact.
It records all the data from the plane and without it, we might never know what happened.
But search teams are now racing against time to find it, as the locator beacon battery will only last around 30 days.
Of course, it may be possible to find it without that locator, but it could potentially be much harder.
When Air France flight 447 disappeared near Brazil, it was a further two years after the first wreckage was found before the black box was recovered.
Malaysia's transport minster said today they would be using "deep sea" search technology in the next phase of the search.
3. Why did none of the passengers communicate before the plane crashed?
Angry family members have repeatedly questioned Malaysian authorities about why it has taken so long to find out where the plane ended up.
How did a plane disappear from all communication channels and fly around seven hours in the opposite direction and no one realised?
If passengers had known they were in trouble, surely they would have tried to make calls or send texts?
Experts have said that flying above 10,000ft and at such speed means no one on board would get a phone signal.
But others have suggested the plane could have been as low as 5,000ft at one stage.
4. Did passengers even know there was something wrong?
Is it possible the passengers didn't realise they were in trouble?
One of the more dramatic theories is that if intervention by the pilot is blamed for this crash, he could of knocked out the rest of the plane by de-pressurising the cabin while he wore an oxygen mask.
Or they may have simply been oblivious to the direction they were flying in.
At 1am in the morning, many of them would have been asleep, and the flight tracker on the passengers' individual screens could also have been disabled.
5. How did no one notice the plane had gone so far off course?
Even if all the passengers were either incapacitated, or unaware something was wrong, how did the plane avoid detection by other radars?
Last week, investigators said MH370's last-known location was to the west of Malaysia.
It is then believed to have flown thousands of miles along a 'southern corridor', deep into the Indian Ocean.
Why was it not picked up in the air space from Malaysia towards the southern Indian Ocean?
6. Were the captain and/or his co-pilot involved?
One of the other few conclusions we have from the Malaysian government, is that they believe the change in flight path was down to "deliberate action" by someone on the plane.
MH370 changed course at least twice from its scheduled route - first to fly west back towards Malaysia and then north west into one of two air lanes used by commercial planes.
Malaysian PM Razak said on March 15: "We can say with a high degree of certainty that the aircraft communications addressing and reporting system was disabled just before it reached the east coast of peninsular Malaysia.
"Shortly afterwards the aircraft's transponder was switched off.
"From this point onwards, the Royal Malaysian Air Force primary radar showed an aircraft believed to be MH370 did indeed turn back. It then flew in a westerly direction back over peninsular Malaysia before turning north west.
"These movements are consistent with deliberate action by someone on the plane."
So the prospect of a hijacking by Captain Zaharie Ahmed Shah, his co-pilot Fariq Hamid or someone else on the plane cannot be completely ruled out.
The fact that all communications were turned off, and the distance the plane travelled, points to someone with piloting experience having been involved.
7. Or could it have been a hijack by a passenger?
If it wasn't one of the pilots, was it someone else?
As mentioned, it had previously been thought it would need to be someone with piloting experience, but some experts think it is possible control of the plane could have been taken by force - either forcing their way through the cockpit door, or someone being invited into the flight deck only to threaten the pilots.
Investigators say terrorism or a mechanical malfunction such as a fire have note been ruled out.
8. Did MH370 crash into the sea after running out of fuel?
It's possible the after flying thousands of miles off course - whether by accident or design - the plane may have crashed into the sea after running out of fuel.
Malaysian authorities have previously said it was only carrying enough to take it on its scheduled mileage.
But whether the plane would have "plunged" or "glided" is also up for debate.
Aviation experts told the BBC that would depend on whether the aircraft was still being flown by a pilot. If so, it could have glided. But if there was no one flying the plane, it could have plunged into the water.