Searchers still have more than 50 percent of 60,000 sq km 'priority area' to investigate

Exactly one year ago, Malaysia Airlines Flight MH370 took off from Kuala Lumpur's airport and subsequently disappeared, leaving the world with one of the greatest aviation mysteries in history.

Four ships, each with a crew of 35 people, are working in 12-hour shifts scanning the southern Indian Ocean floor. Every 45 days, the ships return to Freemantle, Western Australia, to resupply. The round trip takes 12 days.

So far, 26,000 square kilometers of ocean floor have been searched and not a single piece of debris of Flight MH370 has been found.

"I am frustrated like the families and the rest of the team, but we still have more than 50 percent of the search area to go. We need to remember that," said Judith Zielke, chief coordinator of the Joint Agency Coordination Center for the search for Flight MH370.

That 26,000 sq km area is within the 60,000 sq km priority search area set by a group of international experts based on the "handshake" data provided by the satellite provider Inmarsat, and part of a wider search area of 1.1 million sq km.

"The wide search area has remained the same since April last year. It's based on original 'handshake' information released by Inmarsat, which is factual information that cannot be questioned," Zielke said.

"We are confident the aircraft is in that wide search area. Our challenge is to find where. We are talking about an area about two-thirds the size of Australia, and the area we are searching is slightly smaller than Tasmania."

The crews of the ships remain highly motivated by keeping regular contact with families through the JACC, whose job it is to "keep the communications flow".

The search has cost $93 million and has been jointly funded by Australia and Malaysia.

Zielke wouldn't predict what the next step will be if the search of the remainder of the priority area, expected to be completed in May, fails to find any debris, saying it is for the governments of Malaysia, China and Australia to decide after taking into account many possible scenarios.

"You may be aware Australia, through the Australian Transport Safety Board, recently went out with a tender process and asked for an expression of interest from firms around the world to give an indication of what equipment and vessels would be required for a recovery operation," she said.

"Obviously, that information has been thought to be able to inform decisions for governments in relation to what would have to be undertaken in a recovery scenario just as we are also planning for decisions on other scenarios moving forward as well.

"At this moment, we are focused on the priority area and have more than 50 percent of the area still to cover. I remain hopeful we can locate the aircraft in that area."