It is increasingly common for terrorist groups not to claim responsibility for their actions, a leading expert says, amid heightened speculation one or both of the pilots may have been involved in diverting Malaysia Airlines flight MH370.
No trace of the Beijing-bound Boeing 777 has been found since it vanished about an hour after leaving Kuala Lumpur International Airport on March 8 with 227 passengers, including two New Zealanders, and 12 crew aboard.
The search has now been expanded deep into the northern and southern hemispheres. Australian vessels scoured the southern Indian Ocean and China offered 21 of its satellites to help Malaysia in the unprecedented hunt.
Greg Barton, the international director of the global terrorism research centre at Monash University, said there were several reasons a terrorist group might remain silent about hijacking the flight.
''Perhaps this operation was only partially successful, and that the plan had been to turn back and crash into the Petronas Towers in Kuala Lumpur,'' Barton said. ''Perhaps the pilots foiled the plan, we will never know.
''But that would be a motive for a group not to claim it, as they may want to try it again,'' he said.
Zabihullah Mujahid, a spokesman for the Taliban in Afghanistan, who are seeking to oust foreign troops and set up an Islamic state, said the missing plane had nothing to do with them.
"It happened outside Afghanistan and you can see that even countries with very advanced equipment and facilities cannot figure out where it went," he said. "So we also do not have any information as it is an external issue."
A commander with the Pakistani Taliban, a separate entity fighting the Pakistani government, said the fragmented group could only dream about such an operation.
"We wish we had an opportunity to hijack such a plane," he told Reuters by telephone from the lawless North Waziristan region.
But whether it was an act of terrorism remains a question that may not be answered unless the black box flight recorders are found.
Barton cited the 1988 Lockerbie disaster, in which Pan Am flight 103 was destroyed by a bomb over a Scottish town, killing 270 people, as an example of an attack no one admitted ordering.
''It also took quite a while for al Qaeda to claim responsibility for 9/11,'' Barton said. ''And in the November 2008 attacks at several Mumbai hotels, Lashkar-e-Taiba was blamed but never actually claimed it,'' he said.
Clive Williams, a visiting professor at the Australian National University's centre for military and security law and an adjunct professor at Macquarie University's centre for policing, intelligence and counter terrorism said while terrorism could not be ruled out, it seemed less likely than other possibilities.
''Terrorism is by definition politically motivated with a strategic outcome in mind. If terrorism was the motivation you would expect that the perpetrators would have already used the plane as a weapon against a possible target, such as Mumbai or Colombo, would have made political demands, or would have tried to put pressure on a target government.''
Since 2000 there have been only 18 hijacks or attempted hijacks of large passenger aircraft. Of these, seven were by passengers wanting to get to a destination to seek asylum, one was criminally motivated to steal the cargo, six were by mentally ill persons, and four were politically motivated (counting September 11 as one incident), Williams said.
- Sydney Morning Herald