An international land and sea search for a missing Malaysia Airlines MH370 jetliner is covering an area the size of Australia, authorities said on Tuesday, but police and intelligence agencies have yet to establish a clear motive to explain its disappearance.
Investigators are convinced that someone with deep knowledge of the Boeing 777-200ER and commercial navigation diverted Malaysia Airlines Flight MH370, carrying 12 crew and 227 mainly Chinese passengers, perhaps thousands of miles off its scheduled course from Kuala Lumpur to Beijing.
But intensive background checks of everyone aboard have so far failed to find anyone with a known political or criminal motive to hijack or deliberately crash the plane, Western security sources and Chinese authorities said.
Malaysian Acting Transport Minister Hishammuddin Hussein told a news conference the "unique, unprecedented" search covered a total area of 2.24 million nautical miles (7.68 million sq km), from central Asia to the southern Indian Ocean.
Flight MH370 vanished from civilian air traffic control screens off Malaysia's east coast less than an hour after take-off early on March 8.
Investigators piecing together patchy data from military radar and satellites believe that someone turned off the aircraft's identifying transponder and ACARS system, which transmits maintenance data, and turned west, re-crossing the Malay Peninsula and following a commercial aviation route towards India.
Malaysian officials have backtracked on the exact sequence of events - they are now unsure whether the ACARS system was shut down before or after the last radio message was heard from the cockpit - but said that did not make a material difference.
"This does not change our belief, as stated, that up until the point at which it left military primary radar coverage, the aircraft's movements were consistent with deliberate action by someone on the plane," said Hishammuddin. "That remains the position of the investigating team."
BACKGROUND CHECKS CLEAN
China's ambassador to Malaysia said his country had carried out a detailed probe into its nationals aboard the flight and could rule out their involvement.
U.S. and European security sources said efforts by various governments to investigate the backgrounds of everyone on the flight had not, as of Monday, turned up links to militant groups or anything else that could explain the jet's disappearance.
A European diplomat in Kuala Lumpur also said trawls through the passenger manifest had come up blank.
One source familiar with U.S. inquiries said the pilots were being studied because of the technical knowledge needed to disable the aircraft's communications