MH370's captain spoke final words to air traffic control, investigators say

Before you go, we thought you'd like these...
54 PHOTOS
Missing Flight MH370 April 7 going forward
See Gallery
MH370's captain spoke final words to air traffic control, investigators say
In this map provided on Thursday, June 26, 2014, by the Joint Agency Coordination Centre, details are presented in the search for the missing Malaysia Airlines Flight 370 in the southern Indian Ocean. Australian officials say the hunt for the missing plane that vanished during a flight from Kuala Lumpur to Beijing on March 8 with 239 passengers and crew aboard will shift farther south of the most recent suspected crash site in a remote stretch of Indian Ocean. (AP Photo/Joint Agency Coordination Centre) EDITORIAL USE ONLY
This photo illustration shows a journalist looking on the data communication logs from British satellite operator Inmarsat and released by Malaysia's Department of Civil Aviation (DCA) in Kuala Lumpur on missing Malaysia Airlines flight MH370 on May 27, 2014. Malaysia's aviation authority released on May 27 the satellite data used to determine that flight MH370 went down in the southern Indian Ocean following demands from sceptical relatives of those on board. AFP PHOTO / MOHD RASFAN (Photo credit should read MOHD RASFAN/AFP/Getty Images)
A man stands in front of a billboard in support of missing Malaysia Airlines flight MH370 as Chinese relatives of passengers on the missing Malaysia Airlines flight MH370 have a meeting at the Metro Park Hotel in Beijing on April 23, 2014. The hunt for physical evidence that the Malaysia Airlines jet crashed in the Indian Ocean more than three weeks ago has turned up nothing, despite a massive operation involving seven countries and repeated sightings of suspected debris.. AFP PHOTO / WANG ZHAO (Photo credit should read WANG ZHAO/AFP/Getty Images)
In this picture taken May 14, 2014 a Malaysia Airlines staff walks up to a flight prior to departure at the Kuala Lumpur International Airport in Sepang. Malaysia Airlines is expected to announce its first quarter earnings after a bruising period since Flight 370 vanished. AFP PHOTO/ Manan VATSYAYANA. (Photo credit should read MANAN VATSYAYANA/AFP/Getty Images)
In this photo taken on May 5, 2014 the Phoenix Autonomous Underwater Vehicle Artemis Bluefin-21, is shown on the deck of the Australian navy ship Ocean Shield berthed at Fleet Base West near Perth as it prepared to resupply and undertake routine maintenance. Ocean Shield, with the Autonomous Underwater Vehicle on board, was due to head back on May 10 to the remote area of ocean off Western Australia to continue searching for missing Malaysia Airlines Flight MH370. AFP PHOTO / Greg WOOD (Photo credit should read GREG WOOD/AFP/Getty Images)
The attached map shows MH370’s flight path, based on the best available knowledge of the investigation team. There are a number of possible flight paths to the southern Indian Ocean, and three boxes indicating where MH370 likely ended. These flight paths differ based on different projections of the aircraft’s speed, shown on the map in knots.
The attached map shows MH370’s flight path, based on the best available knowledge of the investigation team. There are a number of possible flight paths to the southern Indian Ocean, and three boxes indicating where MH370 likely ended. These flight paths differ based on different projections of the aircraft’s speed, shown on the map in knots.
The attached map shows MH370’s flight path, based on the best available knowledge of the investigation team. There are a number of possible flight paths to the southern Indian Ocean, and three boxes indicating where MH370 likely ended. These flight paths differ based on different projections of the aircraft’s speed, shown on the map in knots.

Photo of a map provided by GeoResonance, which claimed on Tuesday April 29, 2014, that it found wreckage thought to possibly be from missing Flight MH370. The photo was posted to Twitter by user Cristina Lombardi.

GeoResonance A graphic shows images depicting underwater "anomalies" suggesting deposits of various metals #MH370 http://t.co/qi2aUlzE1z

Photo of a map provided by GeoResonance, which claimed on Tuesday April 29, 2014, that it found wreckage thought to possibly be from missing Flight MH370. The photo was posted to Twitter by user Jickson Johnson.

Members of the Malaysia team involved in the search of the Malaysia Airlines MH370 brief relatives of Chinese passengers onboard the missing plane at a hotel in Beijing, China, Tuesday, April 29, 2014. The search team release snippets of the audio between the pilot and the control tower and answered questions relatives has regarding the satellite data used to determine the possible location of the plane. (AP Photo/Ng Han Guan)
PERTH, AUSTRALIA - APRIL 17: A South Korean P3 Orion aircraft takes off from Pearce Airbase, in Bullsbrook, 35 kms north of Perth to help in the search for missing Malaysia Airlines flight MH370 on April 17, 2014 in Perth, Australia. Twenty-six nations have been involved in the search for Malaysia Airlines Flight MH370 since it disappeared more than a month ago. The Malaysian Airways aircraft went missing on 8th March 2014 whilst on a flight between Kuala Lumpur and Beijing. (Photo by Greg Pool - Pool/Getty Images)
From left, Royal Australian Air Force Group Captain Craig Heap, Royal Australian Navy Rear Adm. Greg Sammut, Chris Birrer, Australian Defense Minister David Johnston, Japanese Defense Minister Itsunori Onodera, Japanese Ministry of Defence Director-General Hideshi Tokuchi, Japanese Joint Staff, Vice Chief of Staff Goro Matsumura, Japanese Consul General of Perth Koichi Funayama pose for a photo on the tarmac at RAAF Base Pearce before ahead of Japan's final search flight for the missing Malaysian Airlines flight MH370, Monday, April 28. 2014. Japanese Orion aircraft have logged 46 aerial search missions totaling approximately 400 hours of flight.(AP Photo/Emily Wang)
Ground crew watch as a Japanese P-3C Orion taxis along the tarmac at RAAF Base Pearce before departing for Japan's final search flight for the missing Malaysia Airlines flight MH370, Monday, April 28, 2014. Japanese Orion aircraft have logged 46 aerial search missions totaling approximately 400 hours of flight.(AP Photo/Emily Wang)
A relative of Chinese passengers onboard the Malaysia Airlines MH370 speaks to media as he and others wait for Malaysia embassy staff to meet them outside the Malaysia embassy in Beijing, China Friday, April 25, 2014. About 50 relatives of Chinese passengers on the plane continued a sit-in protest outside the Malaysian Embassy after officials failed to show up to update them on the search. (AP Photo/Andy Wong)
In this map provided on Wednesday, April 23, 2014, by the Joint Agency Coordination Centre, details are presented in the search for the missing Malaysia Airlines Flight 370 in the southern Indian Ocean. The hunt for the missing Malaysia Airlines jet will likely soon deploy more powerful sonar equipment that can delve deeper as the current search of the most likely crash site in the Indian Ocean has failed to yield any clues, Australia's defense minister said Wednesday. (AP Photo/Joint Agency Coordination Centre) EDITORIAL USE ONLY
Relatives of Chinese passengers onboard the Malaysia Airlines Flight 370, cry during a meeting in Beijing Monday, April 21, 2014. Relatives chanted slogans and shouted protests against the lack of meaning answers from Malaysian officials and Malaysia Airlines representatives. (AP Photo/Ng Han Guan)
Relatives of Chinese passengers on board the Malaysia Airlines Flight 370 raise their hands to show their agreement to a decision made during a meeting with Malaysia Airlines staff in Beijing Wednesday, April 23, 2014. Unidentified material that has washed ashore in southwestern Australia is being examined for any link to the lost Malaysian plane, authorities in Australia said Wednesday. (AP Photo/Ng Han Guan)
AT SEA - APRIL 17: In this handout image provided by Commonwealth of Australia, Department of Defence, Phoenix Autonomous Underwater Vehicle (AUV) Artemis begins its dive in the search for the missing Malaysia Airlines Flight MH370 on April 17, 2014. Twenty-six nations have been involved in the search for Malaysia Airlines Flight MH370 since it disappeared more than a month ago. The Malaysian Airways aircraft went missing on 8th March 2014 whilst on a flight between Kuala Lumpur and Beijing. (Photo by LSIS Bradley Darvill/Australia Department of Defence via Getty Images)
In this Monday, April 14, 2014, photo provided by the Australian Defense Force an autonomous underwater vehicle is deployed from ADV Ocean Shield in the search of the missing Malaysia Airlines Flight 370 in the southern Indian Ocean. The search area for the missing Malaysian jet has proved too deep for the robotic submarine which was hauled back to the surface of the Indian Ocean less than half way through its first seabed hunt for wreckage and the all-important black boxes, authorities said on Tuesday. (AP Photo/Australian Defense Force, Lt. Kelli Lunt) EDITORIAL USE ONLY Phoenix Autonomous Underwater Vehicle (AUV) Artemis is craned over the side of Australian Defence Vessel Ocean Shield in the search for missing flight MH370.
In this Monday, April 14, 2014, photo provided by the Australian Defense Force an autonomous underwater vehicle is deployed from ADV Ocean Shield in the search of the missing Malaysia Airlines Flight 370 in the southern Indian Ocean. The search area for the missing Malaysian jet has proved too deep for the robotic submarine which was hauled back to the surface of the Indian Ocean less than half way through its first seabed hunt for wreckage and the all-important black boxes, authorities said on Tuesday. (AP Photo/Australian Defense Force, Lt. Kelli Lunt) EDITORIAL USE ONLY Phoenix Autonomous Underwater Vehicle (AUV) Artemis is craned over the side of Australian Defence Vessel Ocean Shield in the search for missing flight MH370.
In this map provided on Tuesday, April 15, 2014, by the Joint Agency Coordination Centre details are presented in the search for the missing Malaysia Airlines Flight 370 in the southern Indian Ocean. The search area for the missing Malaysian jet has proved too deep for a robotic submarine which was hauled back to the surface of the Indian Ocean less than half way through its first seabed hunt for wreckage and the all-important black boxes, authorities said. (AP Photo/Joint Agency Coordination Centre) EDITORIAL USE ONLY
In this map provided on Monday, April 14, 2014, by the Joint Agency Coordination Centre details are presented in the search for the missing Malaysia Airlines Flight 370 in the southern Indian Ocean. The hunt for the missing Malaysian airliner continued on Monday to focus on a search for weakening radio signals from deep beneath the waves despite evidence mounting that the batteries in the plane’s all-important black boxes may finally have died. (AP Photo/Joint Agency Coordination Centre) EDITORIAL USE ONLY
In this photo taken from the Royal New Zealand air force (RNZAF) P-3K2-Orion aircraft, a RHIB (rigid hull inflatable boat) is deployed from the Australian ship HMAS Perth after it was guided into position by the RNZAF aircraft to recover a red object during a search operation for missing Malaysia Airlines Flight 370, in the Indian Ocean off the coast of western Australia on Sunday, April 13, 2014. The hunt for the missing Malaysian airliner continued to focus Monday on a search for weakening radio signals from deep beneath the waves despite mounting evidence that the batteries in the plane's all-important black boxes may finally have died.(AP Photo/Greg Wood, Pool)
KUALA LUMPUR, MALAYSIA - MARCH 26: Malaysia's Minister of Defence and acting Minister of Transport Hishammuddin Hussein (C) is viewed through a lens as he speaks during a press conference on March 26, 2014 in Kuala Lumpur, Malaysia. The search for flight MH370 resumes today after rought winds and high swells prevented crews from searching for debris yesterday. Six countries have joined the search, now considered to be a recovery effort, after authorities have announced that airliner crashed in the Southern Indian Ocean and that there are no survivors. (Photo by Rahman Roslan/Getty Images)
Malaysia's Minister of Defence and Acting Transport Minister, Hishammuddin Hussein (L) looks at maps as Director General of Civil Aviation Department (DCA) Azharuddin Abdul Rahman (R) answers questions during a press conference at a hotel near Kuala Lumpur International Airport in Sepang on March 17, 2013. An investigation into the pilots of missing Malaysia Airlines flight 370 intensified on March 17 after officials confirmed that the last words spoken from the cockpit came after a key signalling system was manually disabled. AFP PHOTO/ MANAN VATSYAYANA (Photo credit should read MANAN VATSYAYANA/AFP/Getty Images)
US navy captain Mark Matthews (C) speaks with journalists following a media conference involving Angus Houston, head of the Joint Agency Coordination Centre in Perth on April 9, 2014 on the search for missing Malaysia Airlines flight MH370. Australian ship Ocean Shield detected two more signals on April 8 to match a pair of transmissions picked up earlier in the week that have been analysed as consistent with flight data recorder emissions, Angus Houston said. AFP PHOTO / POOL / Greg WOOD (Photo credit should read GREG WOOD/AFP/Getty Images)
Flight MH370's pilot, Capt. Zaharie Ahmad Shah
CANBERRA, AUSTRALIA - APRIL 10 : A handout image released by the Australian Maritime Safety Authority (AMSA) in Canberra, Australia, 10 April 2014, shows the search area and Sonobuoy search area where 14 planes and 13 ships are scouring a 57,923 square km area of ocean for the wreckage of flight MH370 on 10 April 2014.Flight MH370 went missing after losing radio contact with Malaysian and Vietnamese air traffic control after leaving Kuala Lumpur International Airport on March 8. The Beijing-bound flight carried 239 passengers including 12 flight crew from 14 different countries. (Photo by AMSA/Anadolu Agency/Getty Images)
Ben Pelletier, marine operations engineer for Bluefin Robotics, attempts to retrieve a submarine in Quincy, Mass., Wednesday, April 9, 2014. Bluefin Robotics shipped a version of their submarine to help locate the missing Malaysian Airlines Flight 370, by using its side-scan sonar. (AP Photo/Scott Eisen)
A submarine built by Bluefin Robotics is lowered into the water by systems engineer Cheryl Mierzwa in Quincy, Mass., Wednesday, April 9, 2014. Bluefin Robotics shipped a version of their submarine to help locate the missing Malaysian Airlines Flight 370, by using its side-scan sonar. (AP Photo/Scott Eisen)
Ben Pelletier, marine operations engineer for Bluefin Robotics, attempts to retrieve a submarine in Quincy, Mass., Wednesday, April 9, 2014. Bluefin Robotics shipped a version of their submarine to help locate the missing Malaysian Airlines Flight 370, by using its side-scan sonar. (AP Photo/Scott Eisen)
In this April 9, 2014 photo provided by the Australian Defense Force, a Royal Australian Air Force AP-3C Orion flies past Australian Defense vessel Ocean Shield on a mission to drop sonar buoys to assist in the acoustic search of the missing Malaysia Airlines Flight 370 in the southern Indian Ocean. The ship searching for the missing Malaysian jet has detected two more underwater signals that may be emanating from the aircraft's black boxes, and the Australian official in charge of the search expressed hope Wednesday that the plane's wreckage will soon be found. (AP Photo/Australian Defense Force, LSIS Bradley Darvill) EDITORIAL USE ONLY
This image provided by the Joint Agency Coordination Centre on Wednesday, April 9, 2014, shows a map indicating the locations of signals detected by vessels looking for signs of the missing Malaysia Airlines Flight 370 in the southern Indian Ocean. An Australian official overseeing the search for the missing Malaysia Airlines plane said underwater sounds picked up by equipment on an Australian navy ship are consistent with transmissions from black box recorders on a plane. (AP Photo/Joint Agency Coordination Centre) EDITORIAL USE ONLY
Angus Houston (2nd-L), head of the Joint Agency Coordination Centre leading the search for missing Malaysia Airlines flight MH370 speaks at a media conference in Perth on April 9, 2014. Australian ship Ocean Shield detected two more signals on April 8 to match a pair of transmissions picked up earlier in the week that have been analysed as consistent with flight data recorder emissions, Houston said. AFP PHOTO / POOL / Greg WOOD (Photo credit should read GREG WOOD/AFP/Getty Images)
A graphic of the area being searched for missing Malaysia Airlines flight MH370, is displayed during a media conference involving Angus Houston, head of the Joint Agency Coordination Centre in Perth on April 9, 2014. Australian ship Ocean Shield detected two more signals on April 8 to match a pair of transmissions picked up earlier in the week that have been analysed as consistent with flight data recorder emissions, Houston said. AFP PHOTO / POOL / Greg WOOD (Photo credit should read GREG WOOD/AFP/Getty Images)
In this April 7, 2014 photo provided by the Australian Defense Force Able Seaman Clearance Diver Michael Arnold is towed by a fast response craft from the Australian Defense's ship Ocean Shield as he scans the water for debris of the missing Malaysia Airlines Flight 370 in the southern Indian Ocean. Up to 14 planes and as many ships were focusing on a single search area covering 77, 580 square kilometers (29,954 square miles) of ocean, 2,270 kilometers (1,400 miles) northwest of the Australian west coast city of Perth, Australia. (AP Photo/Australian Defense Force, Lt. Ryan Davis) EDITORIAL USE ONLY
In this April 7, 2014 photo provided by the Australian Defense Force Able Seaman Clearance Divers Matthew Johnston, right, and Michael Arnold, from the Australian Defense Vessel Ocean Shield, scan the water for debris from the missing Malaysia Airlines Flight 370 in the southern Indian Ocean. Up to 14 planes and as many ships were focusing on a single search area covering 77, 580 square kilometers (29,954 square miles) of ocean, 2,270 kilometers (1,400 miles) northwest of the Australian west coast city of Perth, Australia. (AP Photo/Australian Defense Force, Lt. Ryan Davis) EDITORIAL USE ONLY
In this April 7, 2014 photo provided by the Australian Defense Force Able Seaman Clearance Diver Matthew Johnston is towed by a fast response craft from Australian Defense's ship Ocean Shield as he scans the water for debris of the missing Malaysia Airlines Flight 370 in the southern Indian Ocean. Up to 14 planes and as many ships were focusing on a single search area covering 77, 580 square kilometers (29,954 square miles) of ocean, 2,270 kilometers (1,400 miles) northwest of the Australian west coast city of Perth, Australia. (AP Photo/Australian Defense Force, Lt. Ryan Davis) EDITORIAL USE ONLY
In this April 7, 2014 photo provided by the Australian Defense Force Able Seaman Clearance Divers Matthew Johnston, right, and Michael Arnold, from the Australian Defense Vessel Ocean Shield, scan the water for debris from the missing Malaysia Airlines Flight 370 in the southern Indian Ocean. Up to 14 planes and as many ships were focusing on a single search area covering 77, 580 square kilometers (29,954 square miles) of ocean, 2,270 kilometers (1,400 miles) northwest of the Australian west coast city of Perth, Australia. (AP Photo/Australian Defense Force, Lt. Ryan Davis) EDITORIAL USE ONLY
In this April 7, 2014 photo provided by the Australian Defense Force a fast response craft manned by members from the Australian Defense's ship Ocean Shield is deployed to scan the water for debris of missing Malaysia Airlines Flight 370 in the southern Indian Ocean. Up to 14 planes and as many ships were focusing on a single search area covering 77, 580 square kilometers (29,954 square miles) of ocean, 2,270 kilometers (1,400 miles) northwest of the Australian west coast city of Perth, Australia. (AP Photo/Australia Defense Force, LSIS Bradley Darvill) EDITORIAL USE ONLY
In this April 7, 2014 photo provided by the Australian Defense Force, a fast response craft manned by members from the Australian Defense's ship Ocean Shield tows Able Seaman Clearance Diver Michael Arnold as they scan the water for debris of the missing Malaysia Airlines Flight 370 in the southern Indian Ocean. Up to 14 planes and as many ships were focusing on a single search area covering 77, 580 square kilometers (29,954 square miles) of ocean, 2,270 kilometers (1,400 miles) northwest of the Australian west coast city of Perth, Australia. (AP Photo/Australian Defense Force, LSIS Bradley Darvill) EDITORIAL USE ONLY
Diagram shows three types of technology used in the search for Malaysia Airlines Flight 370
This image provided by the Joint Agency Coordination Centre on Monday, April 7, 2014, shows a map indicating the locations of search vessels looking for signs of the missing Malaysia Airlines Flight 370 in the southern Indian Ocean. An Australian official overseeing the search for the missing Malaysia Airlines plane said underwater sounds picked up by equipment on an Australian navy ship are consistent with transmissions from black box recorders on a plane. (AP Photo/Joint Agency Coordination Centre) EDITORIAL USE ONLY
Angus Houston, head of the Joint Agency Coordination Centre leading the search for missing Malaysia Airlines flight MH370, points to a graphic of the search area during a media conference in Perth on April 7, 2014. An Australian navy ship has detected new underwater signals consistent with aircraft black boxes, Houston said on April 7, describing it as the 'most promising lead' so far in the month-old hunt for missing Flight MH370. AFP PHOTO / Greg WOOD (Photo credit should read GREG WOOD/AFP/Getty Images)
FILE - In this Sunday, March 30, 2014 file photo, the Australian navy ship Ocean Shield lies docked at naval base HMAS Stirling while being fitted with a towed pinger locator to aid in her roll in the search for missing Malaysia Airlines Flight MH370 in Perth, Australia. Crews searching for the jet launched a targeted underwater hunt on Friday, April 4 for the plane's black boxes along a stretch of remote ocean, with just days left before the devices' batteries are expected to run out. The Ocean Shield, which is dragging a towed pinger locator from the U.S. Navy, and the British navy's HMS Echo, which has underwater search gear on board, will converge along a 240-kilometer (150-mile) track in a desolate patch of the southern Indian Ocean, said Angus Houston, the head of a joint agency coordinating the search. (AP Photo/Rob Griffith, File)
Angus Houston, head of the Joint Agency Coordination Centre leading the search for missing Malaysia Airlines flight MH370, displays a graphic of the search area during a media conference in Perth on April 7, 2014. An Australian navy ship has detected new underwater signals consistent with aircraft black boxes, Houston said on April 7, describing it as the 'most promising lead' so far in the month-old hunt for missing Flight MH370. AFP PHOTO / Greg WOOD (Photo credit should read GREG WOOD/AFP/Getty Images)
Map shows search areas for missing Malaysia Airlines missing jet.; 3c x 5 inches; 146 mm x 127 mm;
A Chinese relative of passengers aboard Malaysia Airlines Flight 370 cries during a mass prayer for the missing plane, in Kuala Lumpur, Malaysia, Sunday, April 6, 2014. The head of the multinational search for the missing Malaysia airlines jet said that electronic pulses reportedly picked up by a Chinese ship are an encouraging sign but stresses they are not yet verified. (AP Photo/Lai Seng Sin)
Chinese Ilyushin IL-76 aircraft flies over Perth towards the international airport returning from search operations for the missing Malaysia Airlines Flight MH370 in Perth, Australia, Sunday, April 6, 2014. Retired Australian Air Chief Marshall Angus Houston, the head of the multinational search, confirmed that a Chinese ship had picked up electronic pulsing signals twice in a small patch of the search zone, once on Friday and again on Saturday, but he stressed the signals had not been verified as linked to the missing plane. (AP Photo/Rob Griffith)
A Chinese Ilyushin IL-76s aircraft taxies past another parked on the tarmac at Perth International Airport after returning from search operations for wreckage and debris of the missing Malaysia Airlines Flight MH370, in Perth, Australia, Monday, April 7, 2014. It’s not a question most governments involved in the hunt for Flight 370 care to answer: How much has the far-flung, month-long search cost? Several Chinese ships and planes have been involved in the search, but China’s foreign ministry did not respond to questions about the expense of the effort. (AP Photo/Rob Griffith)
A man places a LED candle after a mass prayer for passengers onboard the missing Malaysia Airlines Flight MH370, in Kuala Lumpur, Malaysia, Sunday, April 6, 2014. The head of the multinational search for the missing Malaysia airlines jet said that electronic pulses reportedly picked up by a Chinese ship are an encouraging sign but stresses they are not yet verified. (AP Photo/Lai Seng Sin)
of
SEE ALL
BACK TO SLIDE
SHOW CAPTION +
HIDE CAPTION


PERTH, Australia (AP) -- An Australian aircraft Thursday detected what may be the fifth signal coming from a man-made device deep in the Indian Ocean, adding to hopes that searchers will soon pinpoint the object's location and send down a robotic vehicle to confirm if it is a black box from the missing Malaysian jet.

The Australian air force P-3 Orion, which has been dropping sonar buoys into the water near where four earlier sounds were heard, picked up a "possible signal" that may be from a man-made source, said Angus Houston, who is coordinating the search off Australia's west coast.

"The acoustic data will require further analysis overnight," Houston said in a statement.

If confirmed, the signal would further narrow the hunt for Malaysia Airlines Flight 370, which vanished on March 8 while flying from Kuala Lumpur to Beijing with 239 people aboard.

The Australian ship Ocean Shield picked up two underwater sounds on Tuesday, and two sounds it detected Saturday were determined to be consistent with the pings emitted from a plane's flight recorders, or "black boxes."

The Australian air force has been dropping sonar buoys to maximize the sound-detectors operating in a search zone that is now the size of the city of Los Angeles.

Royal Australian Navy Commodore Peter Leavy said each buoy is dangling a hydrophone listening device about 300 meters (1,000 feet) below the surface. Each buoy transmits its data via radio back to the plane.

The underwater search zone is currently a 1,300-square-kilometer (500-square-mile) patch of the ocean floor, and narrowing the area as much as possible is crucial before an unmanned submarine can be sent to create a sonar map of a potential debris field on the seabed.

The Bluefin 21 sub takes six times longer to cover the same area as the pinger locator being towed by the Ocean Shield, and would take six weeks to two months to canvass the current underwater search zone. That's why the acoustic equipment is still being used to get a more precise location, U.S. Navy Capt. Mark Matthews said.

The search for floating debris on the ocean surface was narrowed Thursday to its smallest size yet - 57,900 square kilometers (22,300 square miles), or about one-quarter the size it was a few days ago. Fourteen planes and 13 ships were looking for floating debris, about 2,300 kilometers (1,400 miles) northwest of Perth.

Crews hunting for debris on the surface have already looked in the area they were crisscrossing on Thursday, but were moving in tighter patterns, now that the search zone has been narrowed to about a quarter the size it was a few days ago, Houston said.

Houston has expressed optimism about the sounds detected earlier in the week, saying on Wednesday that he was hopeful crews would find the aircraft - or what's left of it - in the "not-too-distant future."

Separately, a Malaysian government official said Thursday evening that investigators have concluded the pilot spoke the last words to air traffic control, "Good night, Malaysian three-seven-zero," and that his voice had no signs of duress. A re-examination of the last communication from the cockpit was initiated after authorities last week reversed their initial statement that the co-pilot was speaking different words.

The senior government official spoke on condition of anonymity because he wasn't authorized to speak to the media. The conclusion was first reported by CNN.

Investigators suspect the plane went down in the southern Indian Ocean based on a flight path calculated from its contacts with a satellite and analysis of its speed and fuel capacity, but the content of the flight data and cockpit voice recorders is essential to solving the mysteries of why the plane was lost.

The search for the black boxes is increasingly urgent because their locator beacons have batteries that last about a month and may fail soon.

An Australian government briefing document circulated among international agencies involved in the search on Thursday said the acoustic pingers likely would continue to transmit at decreasing strength for up to 10 more days, depending on conditions.

Once there is no hope left of the Ocean Shield hearing more sounds, the Bluefin sub will be deployed.

Complicating matters, however, is the depth of the seafloor in the search area. The pings detected earlier are emanating from 4,500 meters (14,763 feet) below the surface - which is the deepest the Bluefin can dive.

"It'll be pretty close to its operating limit. It's got a safety margin of error and if they think it's warranted, then they push it a little bit," said Stefan Williams, a professor of marine robotics at Sydney University.

The search coordination center said it was considering options in case a deeper diving sub is needed. But Williams suspects if that happens, the search will be delayed while an underwater vehicle rated to 6,000 meters (19,700 feet) is dismantled and air freighted from Europe, the U.S. or Japan.

Williams said colleagues at the Woods Hole Oceanographic Institution in Massachusetts had autonomous and remotely operated underwater vehicles that will dive to 11 kilometers (36,100 feet), although they might not be equipped for such a search.

Underwater vessels rated to 6,500 meters (21,300 feet) could search the seabed of more than 90 percent of the world's oceans, Williams said.

"There's not that much of it deeper than 6 1/2 kilometers," he said.

Williams said it was unlikely that the wreck had fallen into the narrow Diamantina trench, which is about 5,800 meters (19,000 feet) deep, since sounds emanating from that depth would probably not have been detected by the pinger locator.

---

Gelineau reported from Sydney. Associated Press writers Rod McGuirk in Canberra, Australia, and Eileen Ng in Kuala Lumpur, Malaysia, contributed to this report.

Read Full Story

People are Reading