Relatives of flight MH370's passengers and crew have been told that the plane crashed in the southern Indian Ocean, leaving no survivors.
The Malaysia Airlines flight from Kuala Lumpur to Beijing went missing with 239 people on board on March 8, sparking an international hunt for clues to help find it.
Malaysian prime minister Najib Razak announced that data from the UK Air Accidents Investigation Branch (AAIB) and British tracking firm Inmarsat had revealed that MH370's last position was in the ocean west of Perth, Australia.
Mr Razak left no hope for the possibility of survivors, stating that the plane had gone down in a " remote location, far from any possible landing sites".
"It is therefore with deep sadness and regret that I must inform you that according to this new data Flight MH370 ended in the southern Indian Ocean," he said.
Distraught family members who have lost loved ones were informed of the bad news ahead of Mr Razak's press conference in Kuala Lumpur.
Distressing images of relatives who have been staying at a hotel in Beijing during the search were broadcast across the world after they were informed.
"For them the past few weeks have been heartbreaking. I know this news must be harder still," Mr Razak said.
Several satellite images of potential debris in that area had been picked up ahead of the announcement, with French, Australian, American and Chinese authorities all capturing images of possible debris.
The search for debris continued today as two planes from China joined the effort and Australian navy ship, the HMAS Success, was reported to be closing in on the potential wreckage.
But the mystery of what happened to the plane and why remains unsolved ahead of a press conference tomorrow when more details will be revealed.
Since it went missing, experts have speculated about various scenarios - from a terror attack or hijacking, to pilot error or mechanical problems.
China's foreign ministry reportedly said in a statement that it had " demanded that Malaysia provide all information and evidence about how it reached this conclusion".
Although the plane was carrying passengers from 15 nations, most were Chinese citizens.
Meanwhile, Malaysia Airlines denied reports that it had communicated the news to relatives in an English language text message.
A spokesman said in a statement: "Malaysia Airlines did not only send an SMS. The message was conveyed to all families face to face by our top management at the hotels.
"SMS and phone calls were made to those who are not in the hotels via our family support centre. We wanted to ensure that families are informed via all channels."
According to the airline's website, the message sent to relatives read: "Malaysia Airlines deeply regrets that we have to assume that MH370 ended in the Southern Indian Ocean.
"As you will hear in the next hour from Malaysia's Prime Minister, new analysis of satellite data suggests the plane went down in the Southern Indian Ocean."
The airline said that a translation of the message into Chinese was "in progress".
Relatives have previously complained about a lack of information, with some going so far as to threaten a hunger strike as the search dragged on.
Investigators had drawn up two huge search areas in two large arcs - a northern corridor stretching from Malaysia to Central Asia and a southern corridor extending down towards Antartica.
The data analysed revealed that MH370 flew along the southern corridor, based on pings sent several hours after the plane disappeared.
Chris McLaughlin, senior vice president at Inmarsat, told Sky News: "We feel very, very sad and moved for the Chinese and other families that are affected by what seems to have been a major tragedy.
"We obviously take a professional sense of pride in the contribution but we don't diminish for a moment the sadness that will be around the families involved in this."
Mr McLaughlin explained that by comparing information on the pings with data from other Maylasia Airlines flights and other aircraft, investigators were able to rule out the northern corridor as a possibility.
Inmarsat has been the global operator of the Global Maritime Distress and Safety System for 34 years, but Mr McLaughlin said it was the first time it had been asked to locate a lost aircraft or ship based on one single signal.
He said: "Normally you would want to triangulate, often you would have GPS, but because in that region aircraft are not mandated to carry or send out signals of their location we were working from blind, so this is very much a unique approach - the first time it's ever been done."
A spokeswoman for the AAIB said: "As set out by the Malaysian Prime Minister today, we have been working with the UK company Inmarsat, using satellite data to determine the area on which to focus the search.
"We are not able to comment further on this investigation, which is being led by the Malaysian authorities."