140316-N-XY761-019 INDIAN OCEAN (March 16, 2014) Crew members on board a P-8A Poseidon assigned to Patrol Squadron (VP) 16 man their workstations while assisting in search and rescue operations for Malaysia Airlines flight MH370. VP-16 is deployed in the U.S. 7th Fleet area of responsibility supporting security and stability in the Indo-Asia-Pacific. (U.S. Navy photo by Mass Communication Specialist 2nd Class Eric A. Pastor/Released In this handout provided by the U.S. Navy, Crew members on board a P-8A Poseidon assigned to Patrol Squadron (VP) 16 man their workstations while assisting in search and rescue operations for Malaysia Airlines flight MH370 March 16, 2014 in the Indian Ocean. (credit: Mass Communication Specialist 2nd Class Eric A. Pastor/U.S. Navy via Getty Images)

KUALA LUMPUR, Malaysia (CBS News/CBSDC/AP) — The search for the missing Malaysian jet pushed deep into the northern and southern hemispheres Monday as Australia scoured the southern Indian Ocean and Kazakhstan – more than 6,000 miles to the northwest – answered Malaysia’s call for help in the unprecedented hunt.

French investigators arriving in Kuala Lumpur to lend expertise from the two-year search for an Air France jet that crashed into the Atlantic Ocean in 2009 said they were able to rely on distress signals. But that vital tool is missing in the Malaysia Airlines mystery because Flight 370’s communications were deliberately severed ahead of its disappearance more than a week ago, investigators say.

“It’s very different from the Air France case. The Malaysian situation is much more difficult,” said Jean Paul Troadec, a special adviser to France’s aviation accident investigation bureau.

Malaysian authorities say the jet carrying 239 people was intentionally diverted from its flight path during an overnight flight from Kuala Lumpur to Beijing on March 8 and flew off-course for several hours. Suspicion has fallen on the pilots, although Malaysian officials have said they are looking into everyone aboard the flight.

Malaysian police confiscated a flight simulator from the pilot’s home on Saturday and also visited the home of the co-pilot in what Malaysian police chief Khalid Abu Bakar initially said was the first police visits to those homes. But the government – which has come under criticism abroad for missteps and foot-dragging in their release of information – issued a statement Monday contradicting that account by saying police first visited the pilots’ homes as early as March 9, the day after the flight.

Investigators haven’t ruled out hijacking, sabotage, pilot suicide or mass murder, and they are checking the backgrounds of all 227 passengers and 12 crew members, as well as the ground crew, to see if links to terrorists, personal problems or psychological issues could be factors.

The Wall Street Journal has released a report saying “some senior U.S. officials believe that the plane may have been taken as part of a ‘dry run’ for a future terrorist attack, testing the ability to take a plane and hide it from radar and satellites.”

Former Deputy Director of the CIA Mike Morell said it’s a possibility, but it’s unlikely someone would do something of this magnitude as a test.

“If you were able to get control of an aircraft, you would use it immediately,” Morell said.

For now, though, Malaysian Defense Minister Hishammuddin Hussein said finding the plane was still the main focus, and he did not rule out finding it intact.

“The fact that there was no distress signal, no ransom notes, no parties claiming responsibility, there is always hope,” Hishammuddin said at a news conference.

Malaysian Airlines CEO Ahmad Jauhari Yahya said an initial investigation indicated that the co-pilot, Fariq Abdul Hamid, spoke the fight’s last words – “All right, good night” – to ground controllers. Had it been a voice other than that of Fariq or the pilot, Zaharie Ahmad Shah, it would have clearest indication yet of something amiss in the cockpit before the flight went off-course.

CBS News’ Seth Doane rang the doorbell at Fariq’s house over the weekend, but nobody answered. Neighbors told Doane they had seen police cars and motorcycles at the address. A CBS News crew tried Sunday to visit the gated community where Zaharie lives, but the crew was turned away by beefed-up security.

Malaysian officials earlier said those words came after one of the jetliner’s data communications systems – the Aircraft Communications Addressing and Reporting System – had been switched off, sharpening suspicion that one or both of the pilots may have been involved in the plane’s disappearance.

However, Ahmad said Monday that while the last data transmission from ACARS – which gives plane performance and maintenance information – came before that, it was still unclear at what point the system was switched off. That opened the possibility that both ACARS and the plane’s transponders – which make the plane visible to civilian air traffic controllers – were severed later and at about the same time.

Although Malaysian authorities requested that all nations with citizens aboard the flight conduct background checks on them, it wasn’t clear how thoroughly they were conducting such checks at home. The father of a Malaysian aviation engineer aboard the plane, Mohamad Khairul Amri Selamat, 29, said police had not approached anyone in the family about his son, though he added that there was no reason to suspect him.

“It is impossible for him to be involved in something like this,” said the father, Selamat Omar, 60. “He is a good boy … We are keeping our hopes high. I am praying hard that the plane didn’t crash and that he will be back soon.”

Malaysia’s government in the meantime sent out diplomatic cables to all countries in the search area, seeking more planes and ships for the search, as well as to ask for any radar data that might help narrow the task.

Some 26 countries are involved in the search, which initially focused on seas on either side of peninsular Malaysia, in the South China Sea and the Strait of Malacca.

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