Extensive analyses of the satellite pings sent by the plane in its final hours show that it was headed more or less due south until it ran out of fuel. Statistical models show that in theory, it could have ended up anywhere in a 425,000-square-mile area, a swath of ocean about the size of Texas and California combined. Mr. Dolan said that it was "unlikely" the plane was outside the designated search area, however, because analyses of the satellite data suggest the plane was on autopilot as it flew south and made a steep descent at the end, consistent with a plane running out of fuel.
Paul Kennedy, the search director for Fugro, the contractor operating three of the ships, is confident that his vessels can find the aircraft. The company's sonar equipment can detect objects as small as a meter wide, and a 777 extends more than 63 meters, or about 200 feet.
"The technical publications give you confidence that we are looking in the right place," Mr. Kennedy said. "It is just not possible for it to be anywhere else. Too many experts, around the world, independently analyzed the data and came to the same conclusion. These are seriously clever people."
For the relatives of the passengers, a year has been a long time to go without answers. Many complain that the Malaysian and Chinese governments — 153 of the 227 passengers were Chinese — have ignored them.
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"No one is listening," said Steve Wang, whose mother was on the plane and who is an unofficial spokesman for the families in Beijing. "I cannot describe our rage."
Like much of the public, they cannot fathom how, in an era where a missing mobile phone can be located in moments, a wide-body jetliner could simply vanish.
That sense of vulnerability gave new impetus to a long-running debate within the aviation industry over how flights could be tracked more closely in order to help rescuers and investigators respond more quickly in an emergency.
"Flight 370 showed that in today's very connected world, the idea that we cannot know where every airplane is at any given moment has become unacceptable," said Rémi Jouty, the director of the French Bureau of Investigations and Analysis, which has been advising investigators on the case.
French investigators had recommended closer flight tracking measures, including real-time streaming of flight data, in 2012, after a two-year search for the wreckage of an Air France jetliner that crashed in the Atlantic Ocean in 2009. But safety regulators were slow to respond with concrete proposals, viewing the likelihood of a similar event as extremely remote.
But it did happen again. And in the wake of the Flight 370 disappearance, the airlines and the International Civil Aviation Organization, a United Nations body, have agreed in principle on the need for all airliners to have the ability, by November 2016, to automatically report their position at least every 15 minutes, twice as often as the current average of around 30 minutes.
Had those measures been in place before Flight 370 took off from Kuala Lumpur Airport, they may not have prevented the plane from crashing, but the plane would have most likely been found by now and the question of what happened put to rest.
For his part, Mr. Huzlan is reluctant to definitively blame his old friend.
"Despite the trail of logic," he said he could not assume that his old friend "would, on his own accord, for whatever reason, lead 238 others whose lives he was entrusted to hold in his hand to their doom in the depths of the world's loneliest place, the South Indian Ocean."