Nick Grimm reported this story on Thursday, May 29, 2014 18:10:00

MARK COLVIN: After almost 12 weeks of fruitless searching, the international effort to find Malaysia Airlines flight 370 has just taken a giant step backwards.



The Australian Transport Safety Bureau now says the area of the Indian Ocean that's been the focus of the search "can now be discounted as the plane's final resting place".



PM's been told that that means the search area is about to grow 70 times larger. Not only that, but there are no strong clues about where the plane can be located within that much larger area.



And it now seems that acoustic "pings" thought to have come from the plane's black box could even have come from a bar fridge on board the search vessel towing the sonar device.



Nick Grimm reports.



NICK GRIMM: The Australian naval support ship, the Ocean Shield, is now on its way back to Perth, stowed on board the submersible Bluefin-21, which over recent weeks has been scouring an 850 square kilometre area of the Indian Ocean. Its mission for now, formally over.



It's a mission now also formally declared a failure.



Today the joint agency coordination centre which had been overseeing the search for missing Malaysian Airlines plane MH370 released a statement confirming that fact.



EXCERPT FROM JOINT AGENCY COORDINATION CENTRE STATEMENT: No signs of aircraft debris have been found by the autonomous underwater vehicle since it joined the search effort.



The Australian Transport Safety Bureau has advised that the search in the vicinity of the acoustic detections can now be considered complete and in its professional judgement, the area can now be discounted as the final resting place of MH370.



NICK GRIMM: In other words, the international hunt led by Australia has been looking in the wrong place. And what was considered the best lead in the hunt for the missing plane has in fact been a false lead.



Dr Alec Duncan, from the centre for Marine Science and Technology at Curtin University, says it's likely the four acoustic pings that led searchers to concentrate their efforts in that location could have come from a far more mundane source.



ALEC DUNCAN: It's possible that the sounds were generated either by the search vessel itself. Like some, you know, when the bar fridge switches on every now and again, it will create some vibration which will couple through the hull and some of that will end up in the water. There's a whole pile of different pieces of machinery on a ship that operate intermittently so there's, you know, always a possibility of something like that.



Another possibility would be electrical interference from the power supply that's running the pinger detector, or there's a lot of different things. It's actually very difficult to run something like that and be sure that you're not getting interference from something.



NICK GRIMM: The first dissonant note about the acoustic pings came earlier today when a US Naval official told CNN that there was broad agreement that the noises were made by another manmade source most likely from within the ship towing the sonar pinger locator.



The US Navy later contradicted that account saying the comments were "speculative and premature". But it's nevertheless added weigh to the theory that the noises came from within the Ocean Shield or from the pinger device itself.



Alec Duncan again.



ALEC DUNCAN: If the plane was in the area that they searched then they would definitely have found it. The fact that they're searched the area and they've not found the plane means that the plane is not there. So you can be completely sure about that.



NICK GRIMM: The operation will now shift to a much wider search-zone - a 60,000 square kilometre area that will first need to be comprehensively surveyed while tenders are called for from specialist underwater search contractors to explore the sea floor in the area.



Deep-sea explorer and engineer Ron Allum says it's a big task.



RON ALLUM: Yeah, it's just incredible. Just it's a vast, vast area but you're at the limits of the depths of some of those vehicles that they have been using. Let's hope it doesn't go deeper because full ocean depth is a long, long way down below what they're doing already.



NICK GRIMM: But aviation specialists like Peter Marosszeky remain confident that the MH370 will eventually be found.



PETER MAROSSZEKY: From what the evidence thus far has been shown and primarily we have to rely on the Malaysian military's radar systems to confirm that the aeroplane did in fact head in a westerly or south-westerly direction. One would have to say that the aircraft is somewhere in the Indian Ocean but as to where it's very difficult to say.



NICK GRIMM: The man in charge of the search, Angus Houston, did express a lot of confidence that this aircraft would eventually be found, how confident are you that that will be the end result of this massive international operation?



PETER MAROSSZEKY: Look I'm pretty confident that it will but I would also suggest that maybe a piece of information is going to come to light from an unlikely source giving a clue as to where this aircraft might have ended up.



NICK GRIMM: What do you mean by that?



PETER MAROSSZEKY: Well I'm very much of the opinion that the various defence departments of these bigger countries like America and China and Russia, where they're satellite systems are very extensive and very precise, have actually been able to track this aircraft but security precludes them from announcing it because it would disclose their capabilities. It's something that they're very careful not to do.



NICK GRIMM: So you suspect that at this stage someone knows where the aircraft is most likely located but they just don't want to acknowledge that information just yet?



PETER MAROSSZEKY: Yeah that's right, but look I have to admit that I'm basing that on my own experiences. In 1989 when I was with United Airlines we lost our cargo door off flight 811 out of Honolulu at 28,000 feet. And that door was tracked by US satellite then to the bottom of the ocean floor in the Pacific to within 100 metres and a US submersible went down and picked it up.



So in 1989 they had the capability to be able to track a small item like a cargo door to the bottom of the ocean floor and retrieve it, which suggests to me that today, 25 years later, the technology has improved vastly.



MARK COLVIN: Aviation consultant Peter Marosszeky is a senior research fellow with the University of New South Wales. He was speaking to Nick Grimm.