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WHAT’S NEW: Latest On Flight MH370 Mystery

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(CNN) — A 12th day without word on the fate of Malaysian Airlines Flight 370 passed Wednesday, with the frustrated mother of a missing passenger demanding “the truth” from Malaysian authorities. Theories about what happened abound, but many of the facts remain as elusive as the Boeing 777 itself.

Here’s a quick summary of the latest developments, their potential significance and what remains unknown.

What’s new:

A U.S. official familiar with the investigation told CNN that based on present search patterns and available data, it’s far more likely that the plane would be located in the southern arc of the Indian Ocean search area.

Australia said Wednesday that the area of the southern Indian Ocean where it is searching for the plane has been “significantly refined,” based on U.S. data about the jet’s fuel reserves. The search area is centered about 1,600 miles (2,600 kilometers) off Australia’s southwest coast, said John Young of the country’s Maritime Safety Authority.

What it means:

The revised search area is about half the size of the zone Australian authorities had been combing, Young said. But its ships and aircraft have so far seen nothing connected to the missing plane, he said.

“It remains a big area. It’s still very hard to search 300,000 square kilometers (115,000 square miles),” Young said.

And the U.S. official told CNN the search could well last “weeks and not days.”

“This is an area out of normal shipping lanes, out of any commercial flight patterns, with few fishing boats and there are no islands,” he said.

What’s new:

Investigators have discovered that some data had been erased from the flight simulator found in the home of Flight 370’s captain, Zaharie Ahmad Shah, Malaysian authorities reported. Interim Transportation Secretary Hishammuddin Hussein didn’t say what had been deleted, but simulation programs typically store data from previous sessions for later playback. He also did not say who might have deleted the data.

What it means:

The significance of the revelation was unclear. The missing files could reveal the simulator was used to practice diverting the plane and flying it to an unfamiliar airport, experts said. Or it could be another dead end in an investigation that has been full of them so far.

“It may not tell us anything. It’s a step in the process,” one U.S. law enforcement source told CNN. “It could be a very insignificant detail in the process.”

What’s new:

All the jet’s passengers and crew, as well as the ground crew that serviced the aircraft, are under investigation, Hishammuddin told reporters.

What it means:

It’s another sign of the ongoing concerns that Flight 370 may have fallen victim to foul play by someone aboard the aircraft. But after receiving background checks from all nations with passengers on board except Russia and Ukraine, investigators have found no information of significance, Hishammuddin said.

What’s new:

A law enforcement official told CNN that the aircraft’s first major change of course — an abrupt westward turn that took the plane off its planned route to China and back across the Malay Peninsula — was almost certainly programmed by somebody in the cockpit. The change was entered into the plane’s system at least 12 minutes before a person in the cockpit, believed to be the co-pilot, signed off to air traffic controllers; the turn was executed a few minutes later.

What it means:

The timing of Malaysia Airlines Flight 370’s change of direction is a focal point of the investigation into its disappearance. Some experts said the turn could have been part of an alternate flight plan programmed in advance in case of emergency; others suggested it could show something more nefarious was afoot.

Malaysian authorities say the available evidence suggests the missing plane flew off course in a deliberate act by someone who knew what they were doing.

“There is no additional waypoint on MH370’s documented flight plan, which depicts normal routing all the way to Beijing,” Hishammuddin said Wednesday.

And aviation journalist Jeff Weiss told CNN’s “New Day” that the timing of the programming indicates there was no “last-minute panic” to divert to an aircraft because of an emergency, as some people have theorized.

“It’s been almost two weeks now and so little information. We’re grasping at straws. We want to understand,” Weiss said.