The search for the wreckage mustn't be called off, said Grace Nathan (left) shortly before she flew to Madagascar. Her mother was on board flight MH370. The official search is due to be abandoned in February 2017 if nothing is found before then. Relatives of those on board are protesting. "We'll pay for it ourselves," Nathan said. "The search must go on."

In March 2014, for reasons that are still unclear, MH370 deviated from its course from Kuala Lumpur to Beijing and flew south for hours without making radio contact. Investigators believe that the Boeing with 239 people on board went down over the Indian Ocean when its fuel ran out. Experts disagree as to the precise location of the crash.

Some of the passengers' relatives have formed a group called "Voice370." They are critical of the official proceedings. They say "no systematic, organized search" is taking place in the western Indian Ocean, although pieces of wreckage thought to be part of the plane have been found there. Seven of the relatives are now heading to Madagascar, where they themselves plan to search until December 11.

The official search is concentrating on an area of 120,000 kilometers in the southern Indian Ocean. Australia, Malaysia and China are taking part in what is one of the biggest search operations in aviation history. There's been talk of calling it off since the middle of 2016.

On 29 July 2015, a wing flap about two meters long washed up on the tropical French island of La Reunion. The wreckage was subsequently identified as part of the missing Boeing 777. Other possible pieces of wreckage have been found in Tanzania, Mozambique, South Africa and on the island of Mauritius.

At the end of January 2015, Malaysia's civil aviation authority officially classified the unresolved incident an "accident" and declared all 239 people on board dead. But many people don't believe it really was an accident. Relatives have been demonstrating publicly - as here, in China - because they don't feel they're being given all the information.

In July 2015 the New York Magazine reported that a few weeks before the disaster the captain had practiced - on a flight simulator - the route the passenger jet is believed to have taken over the southern Indian Ocean. The magazine cited confidential records from the Malaysian police probe. Despite this discovery, the plane's disappearance remains one of the greatest mysteries in aviation history.

On March 8, Malaysia Airlines Flight MH370 bound for Beijing takes off from Kuala Lumpur International Airport at 12:41 a.m., with 239 people on board. However, 26 minutes after departure, the Aircraft Communications Addressing and Reporting System (ACARS), which transmits key information on the plane's mechanical condition, is switched off.

As the Boeing 777 passes from Malaysian to Vietnamese air traffic control a few minutes later, someone in the plane's cockpit says "Good night Malaysian three seven zero." The airline believes it is co-pilot Fariq Abdul Hamid speaking. The aircraft is flying in good weather conditions.

The plane drops off civilian air traffic control screens as its transponder, which relays information on the plane's location and altitude, is shut down at around 1:31 a.m. As military radar plot the passenger jet at 2:15 a.m., it is located at a point south of the island of Phuket in the Strait of Malacca, hundreds of miles off course.

The aircraft's last communication with satellites seven hours later place it somewhere in one of two corridors: a northern corridor stretching from northern Thailand to the border of Kazakhstan and Turkmenistan, or a southern one stretching from Indonesia to the southern Indian Ocean. The last signal is received at 8:11 a.m., suggesting that the plane may have flown on for hours.

Shortly after the disappearance, Malaysia and Vietnam mount a joint search and rescue mission. The search area is quickly expanded to 100 nautical miles to cover part of the Gulf of Thailand between Malaysia and Vietnam. It also emerges that two passengers had been using stolen EU passports, fueling fears of a terrorist attack. Police later find that the men were illegal Iranian immigrants.

By March 12, the search area for the aircraft encompasses both sides of peninsular Malaysia, over an area of nearly 27,000 square nautical miles (more than 90,000 square kilometers), with a total of 12 countries participating in the operation. A Chinese satellite discovers three large objects floating in the South China Sea that could be debris belonging to the missing airliner.

Two days later, Malaysian PM Najib Razak (seen here right) confirms the plane turned back from its planned flight path and adds the movements "are consistent with deliberate action by someone on the plane." Authorities launch a criminal investigation, refocusing on the crew and the identity and background of the passengers on board. The homes of both the captain and the co-pilot are searched.

Eleven days after the incident, the number of countries involved in the search for the plane increases from 14 to 26, with investigators focusing on the two large corridors the plane may have flown. The search area now covers 2.24 million square nautical miles. French investigators join in to lend expertise from the Air France jet that crashed in the Atlantic Ocean in 2009.

Officials reveal a new timeline suggesting the plane's final voice transmission may have occurred before the communications systems were disabled. Authorities are looking into hijacking, sabotage, or pilot suicide as potential reasons for the disappearance, but background checks of people aboard have yet to point to anyone with a known political or criminal motive to crash or hijack the plane.

Conflicting theories emerge seeking to explain the incident. But without any identified wreckage, it is hard to establish facts. This prolongs the painful wait for the relatives and friends of those who have gone missing. There were people from 14 different countries on board, with the majority of passengers hailing from China (153) and Malaysia (38).

On March 24, Malaysian PM Najib Razak announces that new satellite data suggests Flight MH370 crashed in the southern Indian Ocean with all 239 people aboard presumed dead. The statement unleashes a storm of sorrow and anger among the relatives of the missing. Angry family members - who have complained about a lack of reliable information - demonstrate in front of the Malaysian Embassy in Beijing.

But anticipation repeatedly turns into frustration as objects spotted from planes turn out to be garbage. It's a time-wasting distraction for air and sea crews searching for debris. Sometimes the object traced in the water is a snarled fishing line, a buoy or something that might once have been the lid to an ice box.

On April 3, nearly a month after the flight's disappearance, authorities remain baffled as to how and why it happened. Malaysian Police Chief Khalid Abu Bakar warns that unless the black box is found, the mystery may never be solved. Premier Najib Razak (R) says the search won't stop until answers are found, as his Australian counterpart Tony Abbott calls it "the most difficult in human history."

On April 5, a Chinese vessel reports hearing a "pulse signal" in the Indian Ocean. Two days later, an Australian ship detects two distinct, long-lasting sounds consistent with the pings from aircraft black boxes. The international team subsequently scours roughly 850 square kilometers (330 square miles) of the southern Indian Ocean for weeks, but fails to find any evidence of a wreckage.

In October, Australia shifts the search area further south to where the UK-based satellite company Immarsat calculated the plane probably went down based on brief hourly connections the plane made to one of its satellites. The area, west of Perth, Australia, along a narrow arc in the southern Indian Ocean is identified as the most likely resting place of the jet. But for months nothing is found.

In late January 2015, Malaysia's Department of Civil Aviation officially declared the flight was an accident, and that all people on board were presumed dead. The announcement was in line with global aviation rules that allow families of the passengers to seek compensation. Malaysian officials said they had not ruled out foul play and that the recovery of the missing plane remained a priority.

However, some families of the passengers aboard Flight MH370 refuse to accept Malaysia's conclusion that the plane's disappearance was an accident. Shortly after, Sarah Bajc, whose partner Philip Wood was on the aircraft, tells DW this is a "convenient excuse," arguing that no evidence has been found to support the authorities' claim.

In its efforts to improve global flight safety following the disappearance of MH370, the International Civil Aviation Organization recently proposed a new measure that will require commercial aircraft to report their position every 15 minutes. The guideline is the first stage of a proposal called the Global Aeronautical Distress and Safety System that aims to ensure planes can be tracked quickly.

Chinese families of passengers aboard the flight continue to protest the handling of the search efforts by the Malaysian authorities. They hold prayers and demonstrations on the occasion of the Chinese New Year.

The search teams looking for the missing airliner have so far met many challenges. Some of them are associated with the search area. The remoteness and the size of the area mean that every aspect of the operation must be planned and undertaken meticulously. The search for MH370 is already the most expensive of its kind ever undertaken.