More than 300 flights. Over 3,000 hours in the air. A staggering 4 million square kilometers of ocean.

The numbers speak to the breadth of the search for the missing Malaysia Airlines Flight 370.

The results speak to the fruitlessness of it.

The plane, carrying 239 people, disappeared on March 8. And despite an expansive international search, officials have nothing to show for it.

So authorities are moving on to the next phase of the search -- one that will be even more challenging.

"We know very clearly the area of the follow-up search will be even broader, with more difficulties and tougher tasks," Chinese Transport Minister Yang Chuantang said Monday.

What's next

Australian, Malaysian and Chinese officials will meet in Canberra, Australia, on Wednesday to hash out plans for the next stage of the hunt.

One group will analyze the data and information collected so far. Another will look at the resources needed.

Perhaps the most challenging task: scouring unchartered territory.

Because the next phase will involve an intense underwater search, a key element of the new phase will be a detailed mapping of the ocean floor.

"We know that the water is very deep. And for the next stage .... we need to have an understanding of the ocean floor," Australian Deputy Prime Minister Warren Truss said Monday.

Truss said he's not sure how deep the ocean is in the expanded search area because "it's never been mapped."

The tools

The next stage of the hunt will involved highly specialized technology, including towed side-scan sonar and more autonomous underwater vehicles, Truss said.

"You can count on one hand the number of devices that can do this work, when you talk about towed sonar devices," said Angus Houston, chief coordinator of the joint search effort.

Truss said he's optimistic that the new devices will be in the water within a month or two. In the meantime, he said, the Bluefin-21 drone will continue underwater missions.

The Bluefin-21 has already scanned 40 square kilometers of the Indian Ocean floor, but with no luck. The United States has authorized the use of the drone for another month.

The cost

Australia estimates the next phase of the search will cost about $60 million, Truss said. He said officials will consult with Malaysia, China and other parties on how that cost would be shared.

Until now, all countries involved in the search have paid for their own costs.

"Whenever we've asked, people have come forward," Truss said. But "I think we'll be looking at increasing involvement from the manufacturers and their host countries."

Letting others in

The new phase will allow more parties to join the search, acting Malaysian Transport Minister Hishammuddin Hussein said.

"This gives an opportunity to those not involved in the early phase of the search and rescue efforts to come on board," he said.

Those could involve research institution and more countries, he said.

Lessons learned

It took two years to find the wreckage of Air France Flight 447 in the Atlantic Ocean.

Truss said authorities can learn from that effort.

"There were some quite long gaps in their search, and we don't want that to happen in this instance," Truss said. "That's why we're starting work this week on actually putting together the next stages of the search."

But as officials from this search have already learned, hope can dash as quickly as it arises.

"We've been confident on the basis of the information provided that the search area was the right one," Truss said. "But in practice, that confidence has not been converted into us discovering any trace of the aircraft."