With 260 casualties and only one surviving passenger, the Air India 171 crash is one of the deadliest aviation incidents in recent history — and so far it’s proving to be one of the most frustratingly opaque.

Video of the June 12 incident had previously captured the Boeing 787 taking off successfully from Ahmedabad bound for London, only to rapidly descend, crash into a medical college complex, and explode into flames. The crash killed all but one of the plane’s 242 occupants. It also damaged five buildings, killed 19 people on the ground, and injured over 60 more.

The weeks that followed saw rampant speculation, AI-generated hoaxes, and conspiracy theories. Finally, on July 11 India’s air safety organization, the Aircraft Accident Investigation Bureau (AAIB), issued a preliminary report into the cause of the disaster. The 15-page report pinpointed a dark and disturbing factor as the reason for the crash: Shortly after takeoff, someone or something cut the flow of fuel to both engines, almost simultaneously. This caused a brief but fatal dual engine shutdown that proved impossible for the plane to recover from.

The implications of that double shutdown are quite bleak — but there’s still a lot we don’t know.

What caused the crash?

In the weeks following the tragedy, public speculation about the potential cause ranged from a bird strike to an electrical problem; some suggested fuel contamination, others a malfunction with the wing flaps. Many focused on what seemed to have been an extreme occurrence suggested by the visibility of the Ram Air Turbine (RAT), which deploys when there are engine problems: a total engine failure.

Over on YouTube, many analyzed the crash, including some pilots. Among them was Trevor Smith, call sign “Hoover,” a former military pilot who now flies for a commercial airline. On the side, he runs the YouTube crash analysis channel Pilot Debrief. Following the Air India crash, he emphasized what seemed to be the dual loss of thrust to both engines, and speculated that perhaps one engine had lost thrust for an unknown reason and that then one of the pilots had accidentally turned off the fuel control switch to the other engine, causing both to lose thrust.

Smith was hypothesizing a scenario in which at least one engine had been lost due to a mechanical failure, and an overwhelmed pilot mistakenly deactivated the other engine. The preliminary report, however, was more grim. It rejected all of those possibilities and instead pointed firmly toward a simple but unthinkable event: Both engines were shut down, first one and then the other, by way of the fuel control cutoff switch.

In most Boeing airplanes, the flow of fuel to the engines gets activated via two fuel control switches. In the Boeing 787, the jet fuel control switches sit in the main console of the aircraft just below the throttles (which are used to control thrust power). The fuel switches........

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