PETALING JAYA - The search for Malaysian Airlines MH370 is the longest yet for a commercial flight that has gone missing, and there is still no end in sight.
Flight MH370 took off from KL International Airport at around 12.41am bound for Beijing on March 8, but dropped off the radar soon after take off, leaving authorities struggling to piece together where the aircraft went.
As the search enters its 13th day on Thursday, it has gone past the previous record for a missing commercial airliner, when wreckage for Adam Air Flight 574 was not found until 10 days after it lost contact with air traffic control.
Flight 574, a Boeing 737-400, went missing off the coast of Indonesia's South Sulawesi on Jan 1, 2007.
The first confirmed discovery was by a fisherman who found piece of the plane's tail fin, which had serial numbers matching the missing plane. He received reward of 50mil rupiah (RM14,500) for his discovery.
Where MH370 differs from other instances is the flight path - while most followed the original planned one, the situation is not as clear-cut in MH370's case.
The search for MH370 is now along two corridors, with an area of 2.24 million square nautical miles - an area larger than Australia, which only makes search and rescue efforts even more difficult.
Here are some instances of commercial airliners that did not reach their scheduled destinations, and the search operation to find them.
Adam Air Flight 574: 10 days
On Jan 1, 2007, Adam Air Flight 574, scheduled domestic passenger flight between the Indonesian cities of Surabaya and Manado crashed into the Makassar Strait near Polewali in Sulawesi.
All 102 people on board died, the highest death toll of any aviation accident involving a Boeing 737-400.
A full national investigation was immediately launched into the disaster. The final report, released on 25 March 2008, concluded that the pilots lost control of the aircraft after they became preoccupied with troubleshooting the inertial navigation system and inadvertently disconnected the autopilot.
The black boxes were located on Jan 21, 2007.
Air France Flight 447: Five days
On June 1, 2009 Air France Flight 447 was on a scheduled international flight from Galeão International Airport in Rio de Janeiro, Brazil, to Charles de Gaulle International Airport in Paris, France.
The Airbus A330-203 airliner serving the flight crashed into the Atlantic Ocean, resulting in the deaths of all 216 passengers and 12 aircrew.
The accident was the deadliest in the history of Air France.
It was also the Airbus A330's second and deadliest fatal accident, and its first in commercial passenger service.
While Brazilian Navy authorities were able to locate the first major wreckage and two bodies from the sea within five days of the accident, investigations into the cause of the crash were hampered as the aircraft's black boxes were not recovered from the ocean floor until May 2011, nearly two years later.
EgyptAir Flight 990: One day
On Oct 31, 1999, EgyptAir Flight 990 was a regularly scheduled flight from Los Angeles International Airport, United States to Cairo International Airport, Egypt, with a stop at John F. Kennedy International Airport, New York City.
The Boeing 767-300ER operating the route crashed into the Atlantic Ocean about 60 miles (97 km) south of Nantucket Island, Massachusetts, killing all 217 people on board.
The cause of the crash - either intentional or from mechanical failure - has been disputed.
Search and rescue operations were launched within minutes of loss of radar contact, with the bulk of the operation being conducted by the United States Coast Guard (USCG).
At sunrise, a US Merchant Marine Academy training vessel found an oil sheen and some small pieces of debris.
Rescue efforts continued by air and by sea, with a group of USCG cutters covering 10,000 square miles (26,000 sq km) on Oct 31 with the hope of locating survivors, but no bodies were recovered from the debris field.
The search and rescue operation was eventually suspended on 1 November 1999, with the rescue vessels and aircraft moving instead to recovery operations.
A second salvage effort was made in March 2000 that recovered the aircraft's second engine and some of the cockpit controls.