I already acknowledged this was a speculative line of thought. Don't think any air crash investigators are looking into a nobody on the internet for accident
clues, so it's a kind of very limited irresponsibility.
However there are actually not that many causes, that could explain the vertical drop either than, and in order of decreasing probability:
The accidental deployment of the reverse thrusters, is something
that requires multiple mechanical failures, is not supposed to happen
but Boeing already has a past history with it, although on a different model.
The Niki Lauda/Boeing controversy.
If the reversers open, wouldn't just shutting down the engines lead to a better scenario than this? I recall a 737 gliding too a nearby airport in Canada when it ran out of fuel.
I suppose it depends on whether the crew would have been aware of it.
Can the reversers be opened independently on left and right side? From some of the 3D plots on various threads it looks like the plane took a sharp left before diving. Could it be the left reverser malfunctioned or be accidently opened mid flight causing the plane to swirl left and lose the aerodynamic?
They can. Although incredibly rare. There are a few military airplanes that use reversers in flight to quickly drop altitude, but not used in any commercial passenger airplane that way. That scenario of only one opening, is also addressed in the video from Mentour Pilot that I linked. A few minutes earlier in the video. They have a checklist for it.
However there are actually not that many causes, that could explain the vertical drop either than, and in order of decreasing probability:
- Suicide/Terrorism
- A Jackscrew Mechanism Failure: https://www.wikiwand.com/en/Jackscrew
- Accidental Deployment of the Reverse Thrusters.
The accidental deployment of the reverse thrusters, is something that requires multiple mechanical failures, is not supposed to happen but Boeing already has a past history with it, although on a different model. The Niki Lauda/Boeing controversy.
"What if the reversers OPEN in flight?!"
Video at correct time: https://youtu.be/OguKthkuaT4?t=1026