CANBERRA, Australia (AP) — Not one object has been recovered from the missing airliner that Malaysian officials are now convinced plunged into the southern Indian Ocean 17 days ago. Some of the pieces are likely 3,500 meters (11,500 feet) underwater. Others are bobbing in a fickle system of currents that one oceanographer compares to a pinball machine. And by now, they could easily be hundreds of kilometers (miles) away from each other.
The job of gathering this wreckage, and especially the black boxes that will help determine what happened to Malaysia Airlines Flight 370, is an unprecedented challenge. The crews who needed two years to find a black box from the Air France flight lost in the Atlantic in 2009 had much more information to go on.
"Even though that was the biggest and most complicated search for an aircraft in the ocean ever conducted, it was a relatively refined area compared with what we're talking about here," said U.S. underwater wreck hunter David Mearns, who advised both British and French investigators in the Air France case.
Malaysia said the latest search area had been narrowed to about 870,000 square kilometers (335,000 square miles, 470,000 square nautical miles), an area about as big as Texas and Oklahoma combined.
It was analysis of satellite data, rather than any confirmed wreckage, that led Malaysia to conclude Monday that Flight 370 plunged into the Indian Ocean 2,500 kilometers (1,550 miles) southwest of the Australian west coast city of Perth, and that all 239 people aboard died. Satellites and planes have seen objects in the water, large and small, but nothing has been retrieved or positively identified as coming from the Boeing 777-200.
Geoff Dell, discipline leader of accident investigation at Central Queensland University, said Tuesday that if the black boxes are found, it would be the most difficult search for a lost plane ever to succeed.
"We're not searching for a needle in a haystack," said Air Marshal Mark Binskin, Australia's deputy defense chief. "We're still trying to define where the haystack is."
Dell said there's an urgent need to find any wreckage from the plane. Even one piece would allow oceanographers to plot where it might have drifted from. That information, combined with the vague course of the plane calculated by British satellite company Inmarsat, could greatly refine the search area for pieces that have sunk.
"You've got a rough idea of the flight path from this satellite data. Using your best guesses, you've got to backtrack from where you've fished the pieces out of the water, based on current and wind," Dell said. "You're looking for those two paths to intersect and that would be your starting point, but there'd be many, many variables, estimations and tolerances in both of those paths."
The estimated paths of the flight and the current would produce "an X-marks-the-spot where we start looking, but it could be a couple of hundred miles off," he said.
The job gets harder every day the current carries wreckage away, said Erik van Sebille, an oceanographer at the University of New South Wales in Sydney. He said the swirling and unpredictable nature of currents can spread items that begin in the same place hundreds of kilometers (miles) apart within weeks.
"It's like one giant pinball machine out there," he said.
Weather is further complicating the task. The search was suspended for 24 hours Tuesday due to rough seas.
Binskin, the Australian deputy defense chief, said search planes had dropped electronic buoys near potential debris fields that have been seen in recent days, in hopes of keeping track of them.
Australian Defense Minister David Johnston said, "The turning point for us, I think, will be when we pull some piece of debris from the surface of the ocean and positively identify it as being part of the aircraft."
The search involves ships and planes from the United States, China, Japan, Australia, New Zealand and South Korea.
Malaysia said the U.S. Navy will deliver a black box pinger locator to Perth on Wednesday. The Australian warship that will tow the locator is due to arrive in the search area on April 5. By then, there may be little time left.
By law, the boxes must be able to send those signals for at least 30 days following a crash. But experts say they can continue making noise for another 15 days or so beyond that, depending on the strength of the black box battery.
Hans Weber, the president and owner of TECOP International, a San Diego-based aviation consulting firm, said that if the black boxes are submerged, the effectiveness of the pinging they emit can be affected by variations in water temperature.
He said the ocean can form layers of water that are different temperatures, and that sometimes the pinging can effectively be reflected back by a different layer of water. He said the pinging works best in water that has a uniform temperature.
Dell said if the black boxes were several kilometers (miles) deep, the ships might need to be almost directly over them before the signal could detect them.
If found in deep water, Dell expected that unmanned submarines would be needed to retrieve them. That's how the black box from Air France Flight 447 was retrieved in May 2011, almost two years after the Airbus A330 crashed with the loss of 228 lives.
Mearns, the wreck hunter, said this week that Malaysian plane search is far more complex "because with Air France they knew the flight plan of the plane, the track of the plane, the last known position." The last 280 seconds of the plane's path were unclear, he said, compared to several hours for Flight 370.
And it did not take 17 days to find wreckage from Flight 447. Within five days, more than 100 pieces of debris were found.
Associated Press writer Nick Perry in Wellington, New Zealand, contributed to this report.