How could a modern jumbo jet operated by a national airline simply disappear without a trace, erasing 239 lives in the process? The mystery of Malaysia Flight 370 gripped the world five years ago, with media outlets like CNN obsessing over it for a while. Traces of the aircraft finally began turning up on beaches in and around the Indian Ocean, but the craft itself and the bodies of its passengers have never been located, let alone recovered.

What happened? Writing in The Atlantic, William Langewiesche believes he has deduced the sequence of events that led to the destruction of MH370, and also the culprit — pilot Zaharie Ahmad Shah. Langewiesche’s theory provides a chilling narrative that explains hours of flight data that continued long after radar centers lost touch with the flight:

In truth, a lot can now be known with certainty about the fate of MH370. First, the disappearance was an intentional act. It is inconceivable that the known flight path, accompanied by radio and electronic silence, was caused by any combination of system failure and human error. Computer glitch, control-system collapse, squall lines, ice, lightning strike, bird strike, meteorite, volcanic ash, mechanical failure, sensor failure, instrument failure, radio failure, electrical failure, fire, smoke, explosive decompression, cargo explosion, pilot confusion, medical emergency, bomb, war, or act of God—none of these can explain the flight path.

Second, despite theories to the contrary, control of the plane was not seized remotely from within the electrical-equipment bay, a space under the forward galley. Pages could be spent explaining why. Control was seized from within the cockpit. This happened in the 20-minute period from 1:01 a.m., when the airplane leveled at 35,000 feet, to 1:21 a.m., when it disappeared from secondary radar. During that same period, the airplane’s automatic condition-reporting system transmitted its regular 30-minute update via satellite to the airline’s maintenance department. It reported fuel level, altitude, speed, and geographic position, and indicated no anomalies. Its transmission meant that the airplane’s satellite-communication system was functioning at that moment.

By the time the airplane dropped from the view of secondary—transponder-enhanced—radar, it is likely, given the implausibility of two pilots acting in concert, that one of them was incapacitated or dead, or had been locked out of the cockpit. Primary-radar records—both military and civilian—later indicated that whoever was flying MH370 must have switched off the autopilot, because the turn the airplane then made to the southwest was so tight that it had to have been flown by hand. Circumstances suggest that whoever was at the controls deliberately depressurized the airplane. At about the same time, much if not all of the electrical system was deliberately shut down. The reasons for that shutdown are not known. But one of its effects was to temporarily sever the satellite link.

An electrical engineer in Boulder, Colorado, named Mike Exner, who is a prominent member of the Independent Group, has studied the radar data extensively. He believes that during the turn, the airplane climbed up to 40,000 feet, which was close to its limit. During the maneuver the passengers would have experienced some g‑forces—that feeling of being suddenly pressed back into the seat. Exner believes the reason for the climb was to accelerate the effects of depressurizing the airplane, causing the rapid incapacitation and death of everyone in the cabin.

It’s impossible to excerpt enough from Langewiesche’s lengthy and detailed narrative while respecting “fair use,” so be sure to read it all. Briefly, from that point on, the person in the cockpit had the plane to themselves. Pilots have access to better and more plentiful supplies of oxygen, and the perpetrator would have made sure to have that on before depressurizing and ascending. No one would have had any time to make a run at the cockpit door, nor perhaps any sense at all that they would have needed to do so. As Langewiesche next notes, that would have been the only way to ensure that no one could interrupt his plans. And data shows conclusively that at least one person was alive and operating the plane long after these maneuvers.

So who did all this? Langewiesche discards hijacking as unlikely, given the security built into the cockpit. The lack of any stated intent also makes that scenario unlikely, especially since the significant debris found all around Indian Ocean beaches proves the plane never made it to land — despite having plenty of range to do so.

That leaves either the pilot or the co-pilot as the perpetrator. Langewiesche dismisses the co-pilot as an unlikely suspect; Fariq Hamid was young, happily married, and destined for great things in his career with Malaysia Airlines. Shah (referred to by his first name in Langewiesche’s essay), on the other hand, appears to have been in a personal collapse in the months before the plane’s disappearance:

The truth, as I discovered after speaking in Kuala Lumpur with people who knew him or knew about him, is that Zaharie was often lonely and sad. His wife had moved out, and was living in the family’s second house. By his own admission to friends, he spent a lot of time pacing empty rooms waiting for the days between flights to go by. He was also a romantic. He is known to have established a wistful relationship with a married woman and her three children, one of whom was disabled, and to have obsessed over two young internet models, whom he encountered on social media, and for whom he left Facebook comments that apparently did not elicit responses. Some were shyly sexual. He mentioned in one comment, for example, that one of the girls, who was wearing a robe in a posted photo, looked like she had just emerged from a shower. Zaharie seems to have become somewhat disconnected from his earlier, well-established life. He was in touch with his children, but they were grown and gone. The detachment and solitude that can accompany the use of social media—and Zaharie used social media a lot—probably did not help. There is a strong suspicion among investigators in the aviation and intelligence communities that he was clinically depressed.

What about Zaharie’s reported use of an odd flight simulation on his home computer? The significance of that was dismissed early, but Langewiesche argues persuasively that the dismissal might have been premature. It’s possible that Zaharie left it as “bread crumbs” to explain what took place:

Victor Iannello, an engineer and entrepreneur in Roanoke, Virginia, who has become another prominent member of the Independent Group and has done extensive analysis of the simulated flight, underscores what the Malaysian investigators ignored. Of all the profiles extracted from the simulator, the one that matched MH370’s path was the only one that Zaharie did not run as a continuous flight—in other words, taking off on the simulator and letting the flight play out, hour after hour, until it reached the destination airport. Instead he advanced the flight manually in multiple stages, repeatedly jumping the flight forward and subtracting the fuel as necessary until it was gone. Iannello believes that Zaharie was responsible for the diversion. Given that there was nothing technical that Zaharie could have learned by rehearsing the act on a gamelike Microsoft consumer product, Iannello suspects that the purpose of the simulator flight may have been to leave a bread-crumb trail to say goodbye. Referring to the flight profile that MH370 would follow, Iannello said of Zaharie, “It’s as if he was simulating a simulation.” Without a note of explanation, Zaharie’s reasoning is impossible to know. But the simulator flight cannot easily be dismissed as a random coincidence.

Unfortunately, there still is no definitive explanation for MH370’s disappearance, although Langewiesche is certainly convincing. Until the remains of the plane and its passengers and crew are recovered, we have no way to confirm some of this information. Langewiesche notes that even finding the “black boxes” might not provide much more information, other to corroborate the satellite data on which this theory is based. If Shah offered a vocal valediction in the cockpit, that might be preserved — but if he wanted to give a valediction, why not pick up the microphone and do it instead?

Apart from the details, though, it seems clear that whoever was at the controls of MH370 deliberately caused its destruction, for whatever motive — although the absence of a declaration points pretty strongly toward mental derangement rather than anything political. We can only hope the passengers went as peacefully as Langewiesche suggests.