A new report indicates that Malaysian Air Flight 370, the Boeing 757 that went missing nearly four months ago on a flight from Kuala Lampur to Beijing, may not be anywhere near where searchers have been looking:

MELBOURNE, Australia — As Australia prepares a yearlong search for Malaysia Airlines’ missing Flight 370 in an area of ocean floor the size of Croatia or West Virginia, a government report underscores the lingering uncertainty about where the plane went, noting that it might have fallen in an area of the southern Indian Ocean up to 19 times as large as the new search area.

Warren Truss, Australia’s deputy prime minister, announced plans on Thursday for an exhaustive search of the areas of seafloor with the highest probability of holding debris from the Boeing 777-200, which vanished on March 8 with 239 people aboard. That search is to cover an area totaling 23,000 square miles.

“The search area has at all times been based on the best information,” Mr. Truss said at a news conference in Canberra, heading off questions about why the search area keeps moving.

But a detailed report issued Thursday by the Australian Transport Safety Bureau, the government agency overseeing the search, makes it clear that the plane’s possible crash sites could lie far beyond the new search area.

The new search zone is based on five separate analyses of a series of seven electronic “handshakes” between the aircraft — which disappeared after leaving Kuala Lumpur, Malaysia, for Beijing — and a satellite over the Equator. The five analyses were performed by experts at Boeing, the British satellite company Inmarsat, the French electronics group Thales, the National Transportation Safety Board in the United States and the Defense Science and Technology Organization of Australia.

The search zone encompasses the most probable locations calculated by each of the five teams. But each team also calculated a margin of error around its likeliest location. The new search zone encompasses this margin of error for some of the teams, but not all of them.

It would take an area four times the size of the currently planned search to encompass the margins of error for all five teams, according to the safety bureau’s report.

Parts of the area of the Indian Ocean that are included in this new proposed search area included deep valleys that reach down thousands of feet, which could make any search for wreckage next to impossible. As for what happened, that’s something that can never really be confirmed unless and until wreckage is recovered, but the latest theory seems to circle around the “ghost plane” scenario:

The safety bureau concluded in its report that the most likely scenario was that the aircraft headed south for five hours on autopilot during an “unresponsive crew/hypoxia event.” Hypoxia occurs when a plane loses air pressure and the pilots and others aboard, lacking adequate oxygen, become confused and incapable of performing even basic manual tasks, even while continuing to feel considerable confidence in their own abilities.

Mr. Dolan said on Friday that it was wrong to assume that this phrase meant only that the crew could have been unresponsive because of hypoxia. He said that it referred to crew “incapacitation or hypoxia.”

Asked whether the crew could have been incapacitated by violence, Mr. Dolan said that was among the possibilities. But he declined to list the possibilities or speculate on their likelihood.

The investigation into why the plane went astray is under Malaysia’s authority, he noted, while Australia is only trying to assess the aircraft’s track so as to help find it.

As one industry analyst noted recently, there is strong interest in finding the plane and figuring out what happened if only because the 777-200  is one of the most widely used airplanes in the world (Wikipedia lists the number of 777-200’s  in operation at 85). Given that, it would be helpful to know if there’s some defect or structural flaw that was involved in the apparent crash so that it could be addressed in the planes that are still in operation. As it stands, though, the odds that we’ll ever get a definitive answer seem to be slim indeed. Heck, even CNN has given up on this story.

Update: MH370 was mistakenly referred to as a 757 in the original version of this post. It is, in fact, a 777-200. I’ve updated the post accordingly