The green crosshatched rectangle indicates the new search area. The prior search areas are in gray below. (Source: Australian Maritime Safety Authority)

— The search for missing Malaysia Airlines Flight MH370 shifted to another section of the southern Indian Ocean on Friday after new analysis by investigators indicated that the aircraft was traveling faster than previously thought.

The new search area is 680 miles northeast of where planes and ships have been scouring the waters for any sign of the plane. It is also four times as large as where the search team was looking Thursday, expanding the area being covered from 48,500 square miles to 198,200 square miles, according to the Australian Maritime Safety Authority (AMSA).

The new lead comes from analysis of radar data between the South China Sea and the Strait of Malacca before radar contact was lost, AMSA said. Those data show that the aircraft traveled at a higher speed than investigators thought, therefore used more fuel and possibly traveled less far south, according to the Australians.

Australian officials said the new lead was based on continued analysis of information pieced together from radar and satellite data, as observers try to find the plane, which had 239 people on board when it strayed far from its intended path to Beijing on March 8.

The Australian-led search has spent several days trying to track down debris picked up by various satellites, which have offered the strongest leads in the hunt for the plane. But so far, observers on low-flying planes and on ships have come up short.

What happened to Flight 370?

On Monday, a Thai satellite spotted at least 300 floating objects in the southern Indian Ocean, where authorities say the plane went down almost three weeks ago, a Thai official said Thursday.

The images were taken by the Geo-Informatics and Space Technology Development Agency, a Thai space research agency, and show objects more than
1,600 miles southwest of Perth, Australia, said Anond Snidvongs, executive director of the agency.

“I wouldn’t say the debris is from the Malaysia Airlines flight,” Anond said by telephone from Bangkok, adding that analysts could not be certain. “We just spotted a lot of floating objects.”

He said the items were as small as 6 1/2 feet and as long as 52 1/2 feet. They were seen about 124 miles from where French satellites detected a group of more than
100 objects earlier in the week.

The effort to physically locate debris from the aircraft was hampered Thursday as planes set out in the morning, only to turn back a few hours later because of weather conditions. Five ships continued scouring the section of the southern Indian Ocean where authorities think the flight ended. On Friday morning, the search resumed again with
10 aircraft.

Although the satellite images are inconclusive, they should allow air- and sea-based crews to refine their attempts to locate remnants of the missing plane or its cargo, experts said.

“The floating debris combined with the satellite data are a powerful combination,” said Dave Gallo, who searched the ocean bottom for the black box, or flight recorder, of an Air France flight that went down in the southern Atlantic in 2009.

Even after Malaysia's prime minister confirmed the flight "ended" in the Indian Ocean, many questions still remain. Here's a chronology of the baffling aviation mystery. Updated Mar. 26, 2014. (Gillian Brockell and Kate M. Tobey/The Washington Post)

“That gives them the center of the haystack. Track record shows that an aircraft will be very close to that last known position,” he said.

Aircraft and ships from six countries — Australia, New Zealand, the United States, Japan, China and South Korea — have been trying to cover a nearly 50,000-square-mile search area, a region so far from their base in Perth that planes have enough fuel to search for only two to four hours before turning back.

Between bad weather and the unpredictable interplay of wind and ocean currents, observers have run into a series of dead ends.

Wednesday’s search area, for example, included the location where a French satellite detected signs of 122 objects. Observers saw three items in the area late in the day: two that were likely rope plus a blue object. When planes flew overhead again to take a look, they could not spot them.

Even finding debris that comes from the missing flight is just a first step in unraveling the mystery of what happened to it, Gallo said.

The black box containing cockpit audio and flight data must still be found, and at this point any plane debris may have drifted 10 to 100 miles from the spot of the possible crash site.

“It depends on the speed and direction of the winds and the currents. Sometimes they operate against each other, sometimes with each other and sometimes at angles to each other,” said Gallo. “It’s a complicated set of issues.”

In addition to leading the team from the Woods Hole Oceanographic Institution that found the Air France black box in the Atlantic, Gallo took part in mapping the ocean floor near the current search area.

The underwater terrain there is known as the Southeast Indian Ridge, a portion of an underwater mountain chain known as the Mid-Ocean Ridge.

“It’s a 50,000-mile-long mountain range that wraps around the Earth like the seams of a baseball,” Gallo said of the Mid-Ocean Ridge.

He said the ocean bottom was rolling mountains, more like the Appalachians than the Rockies, with depths from 1 1/2 to 2 1/2 miles.

“The bigger obstacle [to the search] is the sea water above it,” he said, recalling days when the institution’s research vessel plowed along at no more than
1 mph. “You expect to have horrible days more than anything else, just because the winds there are typically howling and the currents are always very strong.”

The search could be running short of time.

“That stuff eventually is going to sink. It’s not going to float forever,” said Ron Carr, a pilot for
39 years before becoming a professor at Embry-Riddle Aeronautical University in Arizona.

The U.S. Navy dispatched more equipment to Australia this week. If plane debris is found and drift calculations sharply narrow the search area to a few dozen miles, the additional equipment can be put to use.

The additional equipment includes a device that can be towed underwater to listen for a “ping” from the plane’s black box and an autonomous underwater vehicle (AUV) akin to an unmanned submarine.

The towed ping locator (TPL) is mounted on a sled on a long tether that limits the towing ship’s speed to about 3 mph. The AUV — a Bluefin 21 — can move slightly faster. Three AUVs were used to search a 40-square-mile area of the Atlantic where the Air France airliner went down. That search took several months.

“Those TPLs on paper are fantastic,” Gallo said. “In practice, if the conditions are right and you have skilled operators, they can be powerful. [However,] the ocean can do a lot of things with sound. For instance, if you know how to use thermal layers in the ocean, you can hide a nuclear submarine from some of the most powerful sonar.”

In the Air France search, he said, a ping locator was towed right over the wreck site but didn’t pick up its signal.

While sonar can pick up the signal of metal objects on the ocean floor, the ping sent out by the emergency beacon attached to the black box will fall silent in a matter of days. The battery that powers it has a life of 30 days, so it is expected to die in early April. Its signal carries for no more than three miles.

Halsey reported from Washington. Gu Jinglu in Beijing contributed to this report.