The official Malaysian account of the last contacts made to and received by Flight MH370 is unraveling. As it does, the sinister interpretations of what happened in the cockpit of the Boeing 777 become less persuasive.

We return to the all-important timeline. Originally, the Malaysians said that the last words from the cockpit—from the copilot, “All right, good night”—were spoken to air traffic controllers as the airplane left Malaysian air space at 1:30am.

This week, that timing was significantly changed to 1:19 a.m.—significantly because it meant that the airplane’s transponder, which identifies the flight and confirms its position, stopped operating at 1:22 a.m., after the voice message and not before. As long as it seemed that that calm voice contact was concealing an already-initiated plan to render the 777 invisible, the flight crew were made to look like prime suspects.

Now the chronology has become even more slippery. This time the issue is the other umbilical link between the airplane and the ground, its Aircraft Communications and Addressing Reporting System (ACARS). Malaysia Airlines Chief Executive, Ahmad Jauhari Yahya confessed to a news conference in Kuala Lumpur late Monday that it was now unclear when the ACARS system had been disabled.

Earlier, Acting Transport Minister Datuk Seri Hishammuddin Hussein had said that ACARS contact was lost at 1:07am, before the last words from the cockpit.

Amazingly, the airline chief now admits: “We don’t know when the ACARS was switched off.” It had, he said, worked normally at 1:07 a.m. but failed to send its next scheduled signal at 1:37 a.m.

Bearing in mind the daily muddle and contradictions of these press briefings, this new picture needs carefully to be parsed.

There is, for example, the big difference between “disabled” and “switched off.” The first could mean that a technical failure could have caused it to stop working. The second means a deliberate act by human hand. You don’t need to be a lawyer to appreciate that there is a big difference in the implications of the two terms—and that their use could be either careless or intentional, or just reveal a group of guys who are unaware of the need for precision.

You have to wonder what happens before these astounding reversals pop out of the mouths of Malaysian officials. Do they conceal backstage arguments involving authority, turf, and alternative interpretations of the data? And since the data seems to be so squishy, where is it coming from? Is it all being filtered before we get to witness this farrago in action?

These fresh reversals are not minor in importance. They are fundamental to getting a grip on just what information is available that can be regarded as dependable, the starting point for any investigation, and fundamental to being able to reconstruct with any confidence what was happening to the 777 as it ceased to follow its normal flight path and began its departure into the vast void.

If the new timing on ACARS is correct, it does help to explain how that system was deployed on the Malaysian 777—sending its status reports every 30 minutes.

These reports are short and compact bursts of data—in both text and code—transmitted to commercial data service centers on the ground. These centers then pass on the content to airline operational bases where, for example, maintenance staff can check whether a spare part should be ready at the airplane’s destination. They are also relayed to Boeing and the manufacturers of the engines, in this case Rolls Royce. Engineers on the ground can also send back short messages to the airplane.

The fact that, in the case of Flight 370, these discrete transmissions took place at 30 minute intervals means that although ACARS was monitoring and digesting pre-determined areas of the 777’s behavior—in a sense, its technical life support systems—it was not in any way able to act as a kind of closed-circuit television camera continually recording events in case of trouble and able to relay that situation to observers on the ground. There is no means of doing that.

It’s a trope of bank heist movies that the bad guys disable or mask the CCTV cameras before they get the loot. But why would anyone seeking to skyjack or otherwise get control of this flight go to the trouble of taking out the ACARS? Knowing the rate of fuel consumption or the state of the hydraulic fluids only every 30 minutes would give no clue to either treachery on the flight deck or a takeover in progress.

Perpetrators of any technical proficiency would expect that their greatest threat would come from outside the airplane, not from within it. They were flying through a busy air corridor to China, watched over by both military and civilian radar. They would have assumed that they needed to get far out over an ocean to elude that. In fact, Malaysians have shown themselves unable to collect and interpret information from their own radar systems with any precision, something that is frustrating aviation accident investigators as well as the intelligence community.

If the role of ACARS in the planning of the disappearing act now seems dubious, that leaves the role of turning off the transponder in serious trouble. Here we still have to believe what the Malaysians are telling us, even though they have successfully muddied the waters on everything else. With so much else crumbling, the transponder lies at the heart of this great mystery. At least, for now.