After days of denials, Malaysian officials abruptly changed their tune today and admitted that Malaysian Air Flight 370’s systems continued to communicate for far longer than they first thought. In fact, it’s far longer than anyone thought. Although the transponders were deliberately turned off, the satellite communications systems continued to send “handshakes” for more than seven and a half hours — 90 minutes longer than the original flight to Beijing was scheduled to last:

Malaysian Prime Minister Najib Razak said Saturday that a missing passenger jet was steered off course after its communications systems were intentionally dismantled and could have potentially flown for seven additional hours.

In the most comprehensive account to date of the plane’s fate, Najib drew an ominous picture of what happened aboard Malaysia Airlines Flight MH370, saying investigators had determined there was “deliberate action by someone on the plane.” …

Though previously U.S. officials believed the plane could have remained in the air for several extra hours, Najib said Saturday that the flight was still communicating with satellites until 8:11 a.m. — seven and a half hours after takeoff, and more than 90 minutes after it was due in Beijing. There was no further communication with the plane after that time, Najib said. If the plane was still in the air, it would have been nearing its fuel limit.

“Due to the type of satellite data,” Najib said, “we are unable to confirm the precise location of the plane when it last made contact with the satellite.”

And this seems rather key to the conclusion that this was no mere accident:

U.S. officials have said that the plane, shortly after being diverted, reached an altitude of 45,000 feet and “jumped around a lot.” But the airplane otherwise appeared to operate normally. Significantly, the transponder and a satellite-based communication system did not stop at the same time, as they would if the plane had exploded, disintegrated or crashed into the ocean.

Najib said on Saturday that the Aircraft Communications Addressing and Reporting System, or ACARS, was disabled just as MH370 reached the eastern coast of Malaysia. The transponder was then switched off, Najib said, as the aircraft neared the border between Malaysian and Vietnamese airspace.

That’s where this gets interesting. Someone on Flight 370 shut off the data-transmission part of ACARS, but not the system itself. Apparently, that’s almost impossible to accomplish, and the person who shut it down on the plane may not have been aware of the difference. ACARS uses an active communication system that “pings” plane systems to see if they have updates, but even if the data-transmission system is shut off, the ACARS system on the plane will still return the ping if it still has power. Flight 370 continued to send return handshakes to those pings for more than seven hours, which means that the flight was still in the air, or on the ground with its engines running.

That makes the problem of search-and-rescue even worse. The potential range for a 777 in the air for 7 hours out of Kuala Lumpur produces a massive area, much of which is covered by military radar in some very tense contexts. No one but Malaysia has acknowledged seeing the plane on its military radar, but the path taken after the transponders were turned off suggests that the pilot knew how to pick his way through those areas.

And that has Malaysia taking a much closer look at Flight 370’s captain:

Malaysian police have begun searching the home of the pilot at the helm of the missing Malaysia Airlines flight MH370, after the country’s prime minister confirmed that the Boeing 777’s communications were deliberately disabled by “someone on the plane”.

Police officers arrived at 53-year-old captain Zaharie Ahmad Shah’s home on the outskirts of Kuala Lumpur shortly after the PM, Najib Razak, finished his dramatic press conference, during which he told reporters new satellite data indicated that MH370 last made contact roughly seven hours after it vanished from civilian radar one week ago.

While the raw satellite footage has helped investigators determine that the plane was still flying long after it lost contact with air traffic control at 1.22am on Saturday 8 March with 239 people on board, it could not discern the aircraft’s exact location, Najib said – putting it anywhere along two possible flight corridors: a northern corridor stretching from Kazakhstan, in central Asia, down to northern Thailand; and a southern corridor stretching from Indonesia towards the southern Indian Ocean.

While authorities had initially focused their investigation on the missing plane on four possible explanations, including possible hijacking, sabotage, or the personal or psychological problems of the crew or passengers, the “new information” that had come to light was forcing investigators to rethink their strategy, Najib said.

“In view of this latest development, the Malaysian authorities have refocused their investigation into the crew and passengers on board,” he told reporters on Saturday.

CNN, whose coverage has been rather hyperbolic, offers a better analysis in this clip, which may have more significance now that Malaysia has begun to focus on deliberate intent. Also, its report on the new developments note that while anyone could have been a hijacker, avoiding hostile radar for so long would have taken a lot of military flight experience:

And the apparent lack of visibility on radar? “Airline pilots are not trained for radar avoidance,” said aviation expert Keith Wolzinger, a former 777 pilot. They like to stay on the radar, because — again — it protects their plane.

Only military pilots, he said, are usually keen on avoiding radar.

This mystery keeps getting stranger and stranger.