KUALA LUMPUR, Malaysia — The mystery of Malaysia Airlines flight 370 deepened even further Saturday as authorities said someone on board the vanished jet made a series of highly technical actions to deliberately hide the plane from modern detection systems.
Malaysia's Prime Minister Najib Razak said that communications on the flight missing since last Saturday were disabled due to "deliberate action by someone on the plane" and that the last known signal from the airliner came more than seven hours after takeoff.
The revelation came amid an intensifying search involving dozens of planes and ships in an ever-widening area where the plane may have gone down. Military and government experts on Saturday pored over satellite and radar data that may shed light on the fate of the plane but so far there is no trace of debris.
Speaking at a news conference in Kuala Lumpur, Razak said investigators were making calculations to try to determine exactly how far the airliner traveled after its last point of contact.
According to new satellite data analyzed by the FAA, NTSB, AAIB and Malaysian authorities, the plane's communications from the Aircraft and Communications Addressing and Reporting System were cut off just before the aircraft reached the east coast of the peninsula of Malaysia, and the aircraft's transponder was turned off shortly thereafter, near the border of Malaysia and Vietnam, he said.
Flight 370 departed from Kuala Lumpur for Beijing at 12:40 a.m. on March 8 with 239 people on board. A multinational search effort involving 14 countries, 43 ships and 58 aircraft has turned up no trace of the Boeing 777, despite an expansive search that has widened with each passing day.
China, where the bulk of the passengers were from, expressed irritation over what it described as Malaysia's foot-dragging in releasing information about the search.
Investigators now have a high degree of certainty that one of the plane's communications systems - the Aircraft and Communications Addressing and Reporting System (ACARS) - was partially disabled before the aircraft reached the east coast of Malaysia, Najib said. Shortly afterward, someone on board switched off the aircraft's transponder, which communicates with civilian air traffic controllers.
Najib confirmed that Malaysian air force defense radar picked up traces of the plane turning back westward, crossing over Peninsular Malaysia into the northern stretches of the Strait of Malacca. Authorities previously had said this radar data could not be verified.
"These movements are consistent with deliberate action by someone on the plane," Najib said.
Although the aircraft was flying virtually blind to air traffic controllers at this point, onboard equipment continued to send "pings" to satellites.
U.S. aviation safety experts say the shutdown of communications systems makes it clear the missing Malaysia Airlines jet was taken over by someone who knew how the plane worked.
To turn off the transponder, someone in the cockpit would have to turn a knob with multiple selections to the "off" position while pressing down at the same time, said John Goglia, a former member of the U.S. National Transportation Safety Board. That's something a pilot would know, but it could also be learned by someone who researched the plane on the Internet, he said.
The Aircraft Communications Addressing and Reporting System (ACARS) has two aspects, Goglia said. The information part of the system was shut down, but not the transmission part. In most planes, the information section can be shut down by hitting cockpit switches in sequence in order to get to a computer screen where an option must be selected using a keypad, said Goglia, an expert on aircraft maintenance.
That's also something a pilot would know how to do, but that could also be discovered through research, he said.
But to turn off the other transmission portion of the ACARS, it would be necessary to go to an electronics bay beneath the cockpit. That's something a pilot wouldn't normally know how to do, Goglia said. The Malaysia plane's ACARS transmitter continued to send out blips that were recorded by satellite once an hour for four to five hours after the transponder was turned off. The blips don't contain any messages or data, but the satellite can tell in a very broad way what region the blips are coming from.
Malaysia's prime minister said the last confirmed signal between the plane and a satellite came at 8:11 a.m. - 7 hours and 31 minutes after takeoff. This was more than five hours later than the previous time given by Malaysian authorities as the possible last contact.
Airline officials have said the plane had enough fuel to fly for up to about eight hours.
The last confirmed communication from the plane to a satellite was 8:11 a.m. Malaysia time, Razak said.
The prime minister said the search for the flight has entered a "new phase," focusing on two possible corridors — a northern corridor from the border of Kazakhstan and Turkmenistan to northern Thailand, and a southern corridor from Indonesia to the southern Indian Ocean.
The prime minister also confirmed reports that circulated earlier this week that the plane veered off its course toward Beijing, turning back westward and crossing over peninsular Malaysia into the northern stretches of the Strait of Malacca.
Razak announced that search operations were ending in the South China Sea and investigators are refocusing their attention on the pilots and passengers aboard Flight 370. He added that Malaysia was "working with the relevant countries to request all information relevant to the search, including radar data."
Razak would not confirm a hijacking.
"Despite media reports that the plane was hijacked, I wish to be very clear: We are still investigating all possibilities as to what caused MH370 to deviate from its original flight path," he said.
Razak also defended Malaysia's handling of the investigation, saying that they have followed up each and every lead.
According to a report by Reuters, authorities searched the home of the pilot shortly after the prime minister's statement.
"For the families and friends of those involved, we hope this new information brings us one step closer to finding the plane," Razak said.
Indian navy ships supported by long-range surveillance planes and helicopters scoured Andaman Sea islands for a third day on Saturday without finding evidence of the missing jet, officials said.
Nearly a dozen ships, patrol vessels, surveillance aircraft and helicopters have been deployed, but "we have got nothing so far," said V.S.R. Murthy, an Indian coast guard official.
The Indian navy's coordinated search has so far covered more than 250,000 square kilometers (100,579 square miles) in the Andaman Sea and the Bay of Bengal "without any sighting or detection," the Defense Ministry said in a statement.
The search has been expanded to the central and eastern sides of the Bay of Bengal, the ministry said.
India intensified the search on Saturday by deploying two recently acquired P8i long-range maritime patrol and one C-130J Hercules aircraft to the region. Short-range maritime reconnaissance Dornier aircraft have also been deployed, the ministry said.
Bangladesh has joined the search effort in the Bay of Bengal with two patrol aircraft and two frigates, said Mahbubul Haque Shakil, an aide of Bangladesh's prime minister, Sheikh Hasina.
Seeing no headway, Malaysian authorities suggested a new search area of 9,000 square kilometers (3,474 square miles) to India along the Chennai coast in the Bay of Bengal, India's Defense Ministry said.
India used heat sensors on flights over hundreds of uninhabited Andaman Sea islands that stretch south of Burma (Myanmar), covering an area 447 miles long and 32 miles wide. Only 37 of 572 are inhabited, with the rest covered in dense forests.
The island chain has four airstrips, but only the main airport in Port Blair can handle a large commercial jet.
Much of the early search has focused east of Malaysia in the South China Sea, where the aircraft last communicated with air-traffic base stations about an hour after departing for Beijing.
Three days ago, six Indian navy and coast guard ships, plus reconnaissance planes, began searching eastern parts of the Andaman Sea. On Friday, they headed west of the Andaman and Nicobar islands near the Bay of Bengal.
There are more than 500 islands in that chain, many of which are richly forested and uninhabited.