The new location is consistent with the plane having traveled south at a speed of about 380 knots after it disappeared from Malaysian radar while over the northern end of the Strait of Malacca, Mr. Farrar said. The area that was checked in April and May, after United States Navy contractors thought they had heard acoustic pings from the aircraft’s “black boxes,” was consistent with a plane limping along at 325 knots.

But Mr. Farrar said that the group of independent experts with whom he was working had assumed a speed of 460 to 470 knots. “We are unclear about why they are driving to a relatively slower solution,” he said.

Two possible explanations are that the authorities believe that the plane went farther west before turning south, or that the plane did not follow a straight path on its trip south, Mr. Farrar said. The international search effort and the group in which Mr. Farrar participates are relying on data from a series of electronic “handshakes” between the plane and a satellite over the Indian Ocean, operated by the company Inmarsat, to calculate arcs for the plane’s final location.

One complicating factor is that an exhaustive search of military, intelligence and commercial satellite imagery from around the world has produced no images of the plane in flight, of any impact or of any explosion, investigators said. Nor are there any images of the ocean surface in the new search area from the first week after the plane disappeared — images that might have been checked for signs of debris.

That lack of images should not be surprising, investigators said, because satellites do not routinely squander their finite capacity for taking and transmitting photos on nearly empty oceans.