Why Is MH370 Search Chief So Optimistic?

Retired Air Chief Marshal Angus Houston is a military man, and military men deal in certainties.

He won't commit himself to say they have found the plane. Not yet. Not until he sees some wreckage for his own eyes.

"How confident are you?" he was asked by an Australian reporter. "50%, 70%, 90%?"

He laughed it off. He wouldn't be drawn. Of course he wouldn't. He's a military man. Certainties, certainties, certainties, remember?

There's no "we think we've found it". In his way of thinking, you've either found it or you haven't.

But they have found it, and he knows it.

You only need to read his demeanour and body posture in the press conferences, and how he has relaxed in recent days.

The Bluefin 21 is hoisted back on board the Australian Defence Vessel Ocean Shield after a successful buoyancy test in the southern Indian Ocean

Crews are searching the southern Indian Ocean

And he's absolutely right not to commit himself. Because he wouldn't just be making a judgement without the full facts, he would be sealing the fate of the 239 people who were on that plane, and he would be telling the families that any remaining hope was now lost.

He will have to do that at some point, in the coming days I suspect, but only when he is ready, only when he is sure.

And that's right.

I think his media management has been top notch.

He has answered all the many detailed questions the media have asked, and built trust.

But there is one thing that has me wondering...

"We're being transparent, we're hiding nothing," he said as he left the podium at the end of a recent press conference.

Angus Houston, Angus Houston, head of the agency looking for MH370

Mr Houston has appeared more relaxed in recent days

Well, I don't quite believe him. There was something that led them to that spot in the Indian Ocean, some clue, some intelligence, something that meant Ocean Shield heard the first pings on the very day the black box batteries were due to start weakening.

Sure, Inmarsat has been recalculating its data and narrowing down the search area, but that alone can't be enough.

They have found the plane's black box, potentially 14,700 ft (4,500m) below the Ocean in the middle of nowhere, and not a single piece of wreckage has been picked up to guide them.