Final ATSB Search Report: The Operational Search for MH370

Executive summary

On 8 March 2014, a Boeing 777 aircraft operated as Malaysia Airlines flight 370 (MH370) was lost during a flight from Kuala Lumpur in Malaysia to Beijing in the People’s Republic of China carrying 12 crew and 227 passengers. The search for the missing aircraft commenced on 8 March 2014 and continued for 1,046 days until 17 January 2017 when it was suspended in accordance with a decision made by a tripartite of Governments, being Malaysia, Australia and the People’s Republic of China.

The initial surface search and the subsequent underwater search for the missing aircraft have been the largest searches of their type in aviation history. The 52 days of the surface search involving aircraft and surface vessels covered an area of several million square kilometres. A sub surface search for the aircraft’s underwater locator beacons was also conducted during the surface search.

The underwater search started with a bathymetry survey which continued as required throughout the underwater search and has mapped a total of 710,000 square kilometres of Indian Ocean seafloor, the largest ever single hydrographic survey. The high resolution sonar search covered an area in excess of 120,000 square kilometres, also the largest ever search or survey of its kind. Despite the extraordinary efforts of hundreds of people involved in the search from around the world, the aircraft has not been located.

Regardless of the cause of the loss of MH370, there were no transmissions received from the aircraft after the first 38 minutes of the flight. Systems designed to automatically transmit the aircraft’s position including the transponder and the aircraft communications addressing and reporting system failed to transmit the aircraft’s position after this time period. Subsequent analysis of radar and satellite communication data revealed the aircraft had actually continued to fly for a further seven hours. Its last position was positively fixed at the northern tip of Sumatra by the surveillance systems operating that night, six hours before it ended the flight in the southern Indian Ocean.

The challenge which faced those tasked with the search was to trace the whereabouts of the aircraft using only the very limited data that was available. This data consisted of aircraft performance information and satellite communication metadata initially, and then later during the underwater search, long-term drift studies to trace the origin of MH370 debris which had been adrift for more than a year, and in some cases, more than two years. The types of data, and the scientific methods used for its analysis, were never intended to be used to track an aircraft or pin point its final location.

On 28 April 2014, the surface search for MH370 coordinated by the Australian Maritime Safety Authority (AMSA) was concluded and the Australian Transport Safety Bureau (ATSB) assumed responsibility for conducting the underwater search for the aircraft. The underwater search area was initially defined at 60,000 square kilometres, and was increased in April 2015 when the Tripartite Governments (Malaysia, Australia and the People’s Republic of China) agreed to expand the search area to 120,000 square kilometres. The primary objective of the underwater search was to establish whether or not the debris field of the missing aircraft was in the area of seafloor defined by expert analysis of the aircraft’s flight path and other information. If a debris field was located, the search needed to confirm the debris was MH370 by optical imaging, and then map the debris field to enable planning for a subsequent recovery operation.

Once underwater search operations commenced in October 2014, the MH370 debris field could potentially have been located at any time. A recovery operation would need to have commenced as soon as possible after the debris field was located and the Tripartite governments had agreed on the next steps. The ATSB's role was therefore to also put in place the arrangements and plans necessary for a rapid recovery operation to occur at short notice.

The underwater search applied scientific principles to defining the most probable area to be searched through modelling the aircraft’s flight path and behaviour at the end of the flight. The flight path modelling was based on unique and sophisticated analysis of the metadata associated with the periodic automated satellite communications to and from the aircraft in the final six hours of the flight. The end-of-flight behaviour of the aircraft, when MH370 was considered to have exhausted its fuel, has been analysed and simulated.

In 2015 and 2016, debris from MH370 was found on the shores of Indian Ocean islands and the east African coastline. The debris yielded significant new insights into how and where the aircraft ended its flight. It was established from the debris that the aircraft was not configured for a ditching at the end-of-flight. By studying the drift of the debris and combining these results with the analysis of the satellite communication data and the results of the surface and underwater searches, a specific area of the Indian Ocean was identified which was more likely to be where the aircraft ended the flight.

The understanding of where MH370 may be located is better now than it has ever been. The underwater search has eliminated most of the high probability areas yielded by reconstructing the aircraft’s flight path and the debris drift studies conducted in the past 12 months have identified the most likely area with increasing precision. Re-analysis of satellite imagery taken on 23 March 2014 in an area close to the 7th arc has identified a range of objects which may be MH370 debris. This analysis complements the findings of the First Principles Review and identifies an area of less than 25,000 square kilometres which has the highest likelihood of containing MH370.

The ATSB’s role coordinating the underwater search involved the procurement and management of a range of sophisticated and highly technical services. Management of the underwater search was aimed at ensuring high confidence in the acquisition and analysis of the sonar search data so that areas of the seafloor which had been searched could be eliminated. A comprehensive program was implemented to ensure the quality of the sonar coverage. A thorough sonar data review process was used to ensure areas of potential interest were identified and investigated.

During the early stages of the procurement, careful consideration was given to the methods available for conducting a large scale search of the seafloor. Water depths were known to be up to 6,000 m with unknown currents and unknown seafloor topography. Search operations would also have to be conducted in poor weather conditions and in a very remote area far from any land mass. Planning focused on selecting a safe, efficient and effective method to search the seafloor in an operation with an indeterminate timeframe.

The mapping of the seafloor in the search area revealed a challenging terrain for the underwater search which used underwater vehicles operating close to the seafloor. While the deep tow vehicles selected as the primary search method proved to be very effective, the seafloor terrain necessitated the use of a range of search methods including an autonomous underwater vehicle to complete the sonar coverage.

The underwater search area was located up to 2,800 km west of the coast of Western Australia and the prevailing weather conditions in this area for much of the year are challenging. Crews on the search vessels were working for months at a time in conditions which elevated the operational risks. The ATSB ensured that these risks to the safety of the search vessels and their crews were carefully managed.

At the time the underwater search was suspended in January 2017, more than 120,000 square kilometres of seafloor had been searched and eliminated with a high degree of confidence. In all, 661 areas of interest were identified in the sonar imagery of the seafloor. Of these areas, 82 with the most promise were investigated and eliminated as being related to MH370. Four shipwrecks were identified in the area searched.

The intention of this report is to document the search for MH370, in particular, the underwater search including; where the search was conducted (and why), how the search was conducted, the results of the search and the current analysis which defines an area where any future underwater search should be conducted. The report also includes a safety analysis which is focused on the search rather than on discussing the range of factors which may have led to the loss of the aircraft.

The Government of Malaysia is continuing work on their investigation of the facts and circumstances surrounding the loss of MH370 aircraft consistent with their obligations as a member State of ICAO. The Malaysian investigation is being conducted in accordance with the provisions of ICAO Annex 13, Aircraft Accident and Incident Investigation.

The search, recovery and investigation of the loss of Air France flight AF447, in the South Atlantic Ocean in 2009, and the loss of MH370 have led to some important learnings related to locating missing aircraft on flights over deep ocean areas. Requirements and systems for tracking aircraft have been enhanced and will continue to be enhanced. Steps are being taken to advance other aircraft systems including emergency locator transponders and flight recorder locator beacons.

The ATSB acknowledges the extraordinary efforts of the hundreds of dedicated professionals from many organisations in Australia and around the world who have contributed their time and efforts unsparingly in the search for MH370.

The reasons for the loss of MH370 cannot be established with certainty until the aircraft is found. It is almost inconceivable and certainly societally unacceptable in the modern aviation era with 10 million passengers boarding commercial aircraft every day, for a large commercial aircraft to be missing and for the world not to know with certainty what became of the aircraft and those on board.

The ATSB expresses our deepest sympathies to the families of the passengers and crew on board MH370. We share your profound and prolonged grief, and deeply regret that we have not been able to locate the aircraft, nor those 239 souls on board that remain missing.