BEIJING--The pings have sputtered out in the multinational search for Malaysia Airlines Flight 370, forcing search crews to deploy an underwater robot to find a plane that’s eluded human efforts.

In a last-ditch effort to find the Boeing 777 and its black box flight recorders, a U.S. Navy submersible vehicle will be used to scan an area in the southern Indian Ocean for debris.

“We haven’t had a single detection in six days, so I guess it’s time to go underwater,” Angus Houston, who heads Australia’s Joint Agency Coordination Center, told a news conference in that country’s western city of Perth on Monday.

The remote-controlled Bluefin-21 was to start sonar scans of the seabed possibly later Monday. That seabed lies about 2.8 miles below the surface of the water, right at the edge of the Bluefin’s operating range, and about 1,360 miles northwest of Perth.

Detection of electronic signals in the area last week raised hopes that search crews would soon find the flight recorders from MH370, a Beijing-bound jet that disappeared more than a month ago with 239 people aboard, two-thirds of whom were Chinese citizens. The flight recorders are vital in determining who or what caused the airliner to veer off course and presumably crash in the southern Indian Ocean.

But in a statement early Monday, the Joint Agency Coordination Center reported that its aircraft and ships had come up empty again Sunday in detecting signals through “sonobuoys.” Given that batteries on black boxes typically lose power after 30 days, some analysts say the search has little choice but to enter a new phase.

“The batteries may not be totally dead but could be so weak as to be undetectable,” said Scott Hamilton, a Seattle-based aviation expert. “Either way, it’s time to move on to the next step.”

Several nations, including China and the United States, are assisting Australia in the search. At least 12 aircraft and 15 ships were scheduled to join Monday’s visual search of 18,390 square miles of ocean, an area roughly the size of Vermont and New Hampshire combined.

Search crews haven’t given up on finding the MH370 black boxes. One possibility is that the flight recorders still have power but are so buried in silt on the ocean floor that they can’t steadily send out pings.

At Monday’s news conference, Houston said an oil slick was found in the area Sunday evening. But he added that it might be several days before the source of the oil could be determined.

The search for MH370, initially led by the government of Malaysia, has been marked by false leads and crushed hopes since the airliner disappeared March 8. Authorities initially thought it had crashed in the South China Sea, but satellite data revealed it had flown off course and likely went down somewhere in the southern Indian Ocean.

Before that course shift, someone on the flight turned off the aircraft’s communications systems. Without recovering the flight recorder, it may never be known why MH370 changed course and who was responsible for the change.

For weeks, Malaysia’s handling of the investigation has come under fire in China, particularly from friends and family of MH370 passengers. China’s travel agencies have reported a steep drop in tourism to Malaysia since the airliner disappeared.

Those strains won’t be helped by the reported kidnapping of a Chinese tourist and a Philippine hotel worker from a Malaysian resort last week. The abductors are thought to be part of Abu Sayyaf, an insurgency group that’s carried out past kidnappings in the area.

“The Malaysian political situation is not stable,” one commenter, Shanghai Liulang Wenying, wrote on Sina Weibo, China’s version of Twitter. “A Malaysian airline is missing. A tourist is kidnapped. It’s better not to go there.”

Hamilton is one aviation expert who was convinced early on that MH370 was the victim of foul play. He remains so as the search enters its 38th day.

“The information coming out of Malaysia, if it is to be believed, about the maneuvers of the airplane certainly support the theory that MH370 was under human command and not some ghost flight or under command of an auto pilot,” Hamilton said in an email exchange with McClatchy.

“I’m absolutely convinced this was a criminal act, as I have been since the second day. I still have no idea whether this was a pilot-induced situation or a cockpit intrusion, although I think a passenger-hijacking seems less and less likely.” (Source: McClatchy)

Story Date: April 15, 2014