The missing Malaysia Airlines passenger jet was more likely to have travelled along a southern course near Australia, and should have been picked up by Australia's Jindalee radar network if it did so, a leading surveillance analyst said.
Investigators have identified two possible corridors for flight MH370 after it emerged its transponders were deliberately turned off and satellite data showed it flew for almost seven hours after veering off course in the Gulf of Thailand.
The southern arc took MH370 over Indonesia and down the Western Australian coast, about 1000km from land.
The northern trajectory goes towards northern Iran, passing through Pakistan and Afghanistan, the heartland of Al Qaeda and multiple Islamic extremist insurgencies.
While the route goes over countries renowned for security instability, the region is covered by multiple radar systems.
"It's hard to believe it could go over northern Thailand undetected. They have extensive radar," said Des Ball, professor of strategic and defence studies at the Australian National University.
There are also radar installations operated by Myanmar, China, India and the US, among others, underneath the northern flight path. In addition, high tech US surveillance satellites also intently monitor the area as part of the war on terror.
"Going over land is more logical but it's hard to see how the plane wouldn't have been detected," said Professor Ball.
Australia has one AP-3C Orion surveillance plane scouring the sea near the Cocos Islands, while the other is operating west of Malaysia, chief of the defence force General David Hurley said on Sunday.
There had been more than 50 hours of search time by the planes so far, he added.
But Defence declined to confirm whether its radar and surveillance assets were also being deployed to help the search for the missing plane, which vanished over the Gulf of Thailand with 239 people on board at 1.07am on March 8.
Professor Ball said the reach of Australia's powerful Jindalee over-the-horizon radar is 3000km and could be expected to have picked up the Boeing 777 jet as it traversed Indonesia on any southern route.
However, whether Jindalee, which targets beyond northern Australia, could precisely identify the plane is another matter, as it would have appeared as "just a dot on the screen", said Professor Ball.
Professor Ball said that MH370 data received by the satellite hovering over the Indian Ocean was basic, little more than a ping that could only be used to identify the two possible routes, the mirror image of each other in a 180 degree arc.
The last transmission came at 8.11am on March 8, when the plane would be about to run out of fuel.
Australia to expand assistance
Australia has redeployed a surveillance aircraft searching for the missing jet, Prime Minister Tony Abbott said on Monday.
Mr Abbott said he would be speaking with Malaysia later on Monday to ask what additional assistance Australia could offer to the investigation, which has been refocused to a vast area stretching from the border of Central Asian countries Kazakhstan and Turkmenistan to northern Thailand and a southern corridor stretching from Indonesia to the southern ocean.
Australia had two AP-3C Orion surveillance planes assisting with the search, now in its second week,
“One of our Orions as I understand it has been redeployed to the Indian Ocean search,” Mr Abbott said.
“We've got two Orions which have been assisting with the search.
“They remain available to assist in whatever way the Malaysian authorities wish and it's my intention to talk later today with the Malaysians to see if there's additional help that Australia can offer.”
Mr Abbott said there would lessons for regional security from the incident and “I dare say some of those lessons will involve the tracking of aircraft”.
“At this point I think it's too soon to speculate,” he said.
“We've had a system which has worked pretty well up till now. We've suddenly had an incident, a terrible incident.
“It remains a profound mystery as to precisely what happened.
“Let's as far as we can get to the bottom of it and then decide whether there's anything that ought to be done differently.”