Malaysia Airlines Flight 370

==== Initial search ====
From 18 to 27 March 2014, the search effort focused on a {{convert|315000|sqkm|abbr=on}} area about {{convert|2600|km|nmi mi|abbr=on}} southwest of Perth.<ref name="Search map 19 March"/> The search area, which Australian prime minister [[Tony Abbott]] called "as close to nowhere as it's possible to be", is renowned for its [[Roaring Forties|strong winds]], inhospitable climate, hostile seas, and deep ocean floors.<ref name="AutoVQ-17"/><ref name="Search map 18 March"/> Satellite imagery of the region was analysed;<ref>{{cite web|url=https://thewest.com.au/news/australia/perth-remote-sensing-firm-on-mh370-mission-ng-ya-368670|title=Perth remote sensing firm on MH370 mission|date=3 April 2014|website=The West Australian|access-date=10 December 2019|archive-date=7 December 2019|archive-url=https://web.archive.org/web/20191207035233/https://thewest.com.au/news/australia/perth-remote-sensing-firm-on-mh370-mission-ng-ya-368670|url-status=live}}</ref> several objects of interest and two possible debris fields were identified on images made between 16 and 26&nbsp;March. None of these possible objects were found by aircraft or ships.<ref name="BBC-satellite debris">{{cite news|title=Flight MH370: Images of ocean debris|url=https://www.bbc.com/news/world-asia-26662641|access-date=10 November 2014|publisher=BBC News|date=28 March 2014|archive-date=21 March 2015|archive-url=https://web.archive.org/web/20150321143007/http://www.bbc.com/news/world-asia-26662641|url-status=live}}</ref>

Revised estimates of the radar track and the aircraft's remaining fuel led to a move of the search {{convert|1100|km|nmi mi|abbr=on}} northeast of the previous area on 28&nbsp;March,<ref name="BBC_2014-03-28_b"/><ref name="NST(28 March)"/><ref name="CNN(28 March)"/> which was followed by another shift on 4 April.<ref name="JACC_2014-04-04_mr006">{{cite web|title=Search and recovery continues for Malaysian flight MH370 (4 April 2014 am)|url=http://www.jacc.gov.au/media/releases/2014/april/mr006.aspx|publisher=[[Joint Agency Coordination Centre]]|date=4 April 2014|access-date=6 May 2014|archive-date=5 May 2014|archive-url=https://web.archive.org/web/20140505071902/http://www.jacc.gov.au/media/releases/2014/april/mr006.aspx|url-status=live}}</ref><ref name="Search map 4 April">{{cite web|url=https://s3-ap-southeast-2.amazonaws.com/asset.amsa.gov.au/MH370+Day+18/Charts/2014_04_04_cumulative_search_handout.pdf|title=Incident 2014/1475 – search for Malaysia Airlines flight MH370 – area searched (4 April)|publisher=Australian Maritime Safety Authority|date=4 April 2014|access-date=12 April 2015|archive-date=4 March 2016|archive-url=https://web.archive.org/web/20160304035159/https://s3-ap-southeast-2.amazonaws.com/asset.amsa.gov.au/MH370+Day+18/Charts/2014_04_04_cumulative_search_handout.pdf|url-status=live}}</ref> Between 2 and 17 April, an effort was made to detect the [[underwater locator beacon]]s (ULBs, informally known as "pingers") attached to the aircraft's [[flight recorder]]s, because the beacons' batteries were expected to expire around 7 April.<ref name="BBC_2014-03-31_a">{{cite news|last=Donnison|first=Jon|title=Malaysia flight MH370: No time limit on search, says Tony Abbott|url=https://www.bbc.co.uk/news/world-asia-26814929|work=BBC News|date=31 March 2014|access-date=8 May 2014|archive-date=3 April 2014|archive-url=https://web.archive.org/web/20140403095926/http://www.bbc.co.uk/news/world-asia-26814929|url-status=live}}</ref><ref name="British submarine">{{cite web |url=http://news.sky.com/story/1235477/royal-navy-submarine-joins-mh370-search |title=Royal Navy Submarine Joins MH370 Search |date=2 April 2014 |access-date=12 April 2015 |publisher=Sky News |archive-date=7 July 2015 |archive-url=https://web.archive.org/web/20150707163000/http://news.sky.com/story/1235477/royal-navy-submarine-joins-mh370-search |url-status=live }}</ref> Australian naval cutter [[ABFC Ocean Shield|ADV ''Ocean Shield'']], equipped with a [[towed pinger locator]] (TPL), joined China's ''[[Haixun 01]]'', equipped with a hand-held hydrophone, and the Royal Navy's [[HMS Echo (H87)|HMS ''Echo'']], equipped with a hull-mounted hydrophone, in the search.<ref name=ATSB />{{Rp|11–12}}<ref name="ATSB Final Report AE-2014-054"/>{{rp|36}}<ref name="BBC_2014-03-31_a"/><ref name=20140404IBT>{{cite web | url=http://www.ibtimes.com/malaysia-airlines-flight-mh370-towed-pinger-locators-deployed-underwater-hunt-black-1567381?ft=74gk7 | title=Malaysia Airlines Flight MH370: Towed Pinger Locators Deployed, Underwater Hunt For Black Box Launched With Hopes Of A Breakthrough | website=International Business Times | date=4 April 2014 | access-date=23 March 2018 | first1=Suman | last1=Varandani | archive-date=24 March 2018 | archive-url=https://web.archive.org/web/20180324041402/http://www.ibtimes.com/malaysia-airlines-flight-mh370-towed-pinger-locators-deployed-underwater-hunt-black-1567381?ft=74gk7 | url-status=live }}</ref><ref name="JACC_2014-04-04_mr007">{{cite web|title=Pinger locator equipment commences operation (4 April 2014)|url=http://www.jacc.gov.au/media/releases/2014/april/mr007.aspx|publisher=[[Joint Agency Coordination Centre]]|date=4 April 2014|access-date=6 May 2014|archive-date=31 May 2014|archive-url=https://web.archive.org/web/20140531173951/http://www.jacc.gov.au/media/releases/2014/april/mr007.aspx|url-status=live}}</ref> Operators considered the effort to have little chance of success<ref name="wday95224">{{cite web|url=http://www.wday.com/event/article/id/95224/group/News/ |title=Only days left before Malaysia airlines flight 370's black box dies |publisher=WDAY |date=30 March 2014 |archive-url=https://web.archive.org/web/20140407072117/http://www.wday.com/event/article/id/95224/group/News/ |archive-date=7 April 2014 |url-status=dead |access-date=13 July 2014 }}</ref> given the vast search area and the fact that a TPL can only search up to {{convert|50|mi2|order=flip|km2|abbr=on}} per day.<ref name="wday95224"/>

Between 4 and 8&nbsp;April, several acoustic detections were made that were close to the frequency and rhythm of the sound emitted by the flight recorders' ULBs; [[Search for Malaysia Airlines Flight 370#Underwater locator beacons|analysis of the acoustic detections]] determined that, although unlikely, the detections could have come from a damaged ULB.<ref name=ATSB />{{Rp|13}} A sonar search of the seafloor near the detections was carried out between 14&nbsp;April and 28&nbsp;May but yielded no sign of Flight 370.<ref name=ATSB />{{Rp|14}} In a March 2015 report, it was revealed that the battery of the ULB attached to Flight 370's flight data recorder may have expired in December 2012 and thus may not have been as capable of sending signals as would an unexpired battery.<ref>{{cite news |url=https://phys.org/news/2015-03-mh370-underwater-beacon-battery-expired.html |title=MH370 report: Underwater locator beacon battery had expired |work=phys.org |last=Ng |first=Eileen |date=8 March 2015 |access-date=7 July 2017 |archive-date=14 October 2017 |archive-url=https://web.archive.org/web/20171014234441/https://phys.org/news/2015-03-mh370-underwater-beacon-battery-expired.html |url-status=live }}</ref><ref>{{cite web |first=Samantha |last=Hawley |title=Malaysia Airlines MH370: Report finds battery powering locator beacon on black box expired in 2012, no red flags raised over crew or aircraft |date=8 March 2015 |access-date=8 March 2015 |website=Australian Broadcasting Corp. |url=http://www.abc.net.au/news/2015-03-08/mh370-report-says-black-box-locator-beacon-expired/6289462 |archive-date=8 March 2015 |archive-url=https://web.archive.org/web/20150308132611/http://www.abc.net.au/news/2015-03-08/mh370-report-says-black-box-locator-beacon-expired/6289462 |url-status=live }}</ref>