While families of those on board missing Malaysia Airlines flight MH370 have been given the heartbreaking news that it crashed, the cause of the aircraft's fate remains a mystery.
New data may have been able to confirm that the flight ended in the southern Indian Ocean, but what led to its demise and that of the 239 people on board is still yet to be discovered.
Since the plane went missing, experts have speculated on various theories - from a terror attack or hijacking, to pilot error or mechanical problems.
Owen Geach, commercial director of the International Bureau of Aviation, said he had originally given four theories - adverse weather conditions; catastrophic mechanical or electrical failure of the aircraft; an explosion or terror attack mid-air; or the plane had been forced to land, again by terrorists.
He said since then, pilot suicide had also been suggested as a possible cause, and said that although a forced landing could not be ruled out in the light of today's information, it remains unknown what caused the flight to crash.
He said: "We can now rule out the forced to land theory but that still leaves the other three and ... the possibility of pilot suicide has been suggested.
"The search teams will now need to quickly try to locate the black boxes which will give the best chance of determining probable cause."
In the early days of the flight going missing, speculation surrounded a possible terror attack as police revealed one of the passengers had used a stolen passport.
Malaysian police chief Tan Sri Khalid Tan Sri said one of the passengers using a stolen passport on the missing plane was an Iranian asylum seeker who was not believed to be a member of a terrorist group, and it was thought the 19-year-old was planning to reach Germany.
The stolen passports belonged to Christian Kozel of Austria and Luigi Maraldi of Italy and were entered into Interpol's database after they were taken in Thailand in 2012 and 2013.
Police said a travel agent in the Thai beach resort of Pattaya was contacted by an Iranian man known only as Mr Ali to book one-way tickets for the flight with those names.
The Malaysia Airlines plane did not make a distress call - with one possible explanation that it was blown up by a suicide bomber or a deadly device planted in luggage.
Hijacking was also a possibility, with the disappearance of the Malaysia Airlines plane possibly explained by passengers storming the cockpit as happened on board United Flight 93 during the September 11 attacks in the United States.
Malaysia's air force chief, Rodzali Daud, has said radar indicated that the plane may have turned back, which could suggest engine failure or an electrical malfunction.
Another theory is human error, although the 53-year-old pilot, Zaharie Ahmad Shah, has more than 18,000 flying hours and has been flying for the airline since 1981, while the first officer, 27-year-old Fariq Hamid, has about 2,800 hours of experience and has flown for the airline since 2007.
And while a catastrophic failure of the aircraft is another possibility, the Boeing 777 has a good safety record, while Malaysia Airlines has an excellent safety record as well.