OK…48 Hour Rule applies. I am completely speculating here with almost no evidence to back this up. That said, even at this early hour, there is evidence to look at.

There is a YouTube which couples the position of the aircraft in question…N722BD… with the radio transmissions from the aircraft. I have listened to it twice, and that’s all I can stomach. I recommend that if this is new to you that you turn your audio off, and I’ll give you what I can. [Also note that there are portions of this YouTube that VAS has appeared to have sped up. What you’re seeing here isn’t necessarily how it happened in real time.]

The data tag for each aircraft that is shown to the ATC controller has several parts to it. The top line shows the identifier of the plane. Since this was a private plane, the identifier is the plane’s tail number….N722BD. In a radio call, this will often be shortened to “2BD” or maybe “22BD”. Underneath that you will see 3 digits representing the plane’s altitude. The beginning of this video shows that N722BD was at “410” or 41,000′ above sea level.

• At 1:33 N722BD gets cleared to descend to Flight Level 350….35,000′.
• At 1:39, they get cleared to deviate from their course, left or right, and when done deviating, then proceed direct to Freeport. They are descending through 39,500′.
• At 2:02, you get a warning that what follows is explicit, and again, I encourage you to turn your audio off.
• At 2:19, they report light clear ice…”manageable”…and moderate turbulence. They are at FL350.
• At 2:36, ATC reports that they didn’t hear that transmission and asks who it was.
• At 2:40, 22BD reports that it was them and adds “plus or minus…700, 600 feet” [More on this below].
• At 3:22, they either enter or are above a thunderstorm cell and ask to climb to FL370. They are at FL351.
• ATC gives them the clearance to climb, and they make it as high as FL354 before they start to descend.
• At 3:45, 22BD declares an Emergency with “Mayday, Mayday” and says that they are descending at 10,000 feet per minute. They have 3 and a half minutes to solve this problem.
• At 3:56, 22BD reports an overspeed condition. They’re going faster than the aircraft is certified to handle.
• At 4:12, 22BD reports that they’re going to crash into the ground.
• At 4:20, 22BD reports that they are descending through 22,000′ (I’m infering “through” although a descent rate of 22,000 feet per minute is possible too) and are at 60° of bank.
• At 4:45, the data block hangs up reporting an altitude of 8900′. I suspect that this is a artifact of the ATC system. The data block drops off the screen at 5:05 and there are no further radio transmissions.

Thunderstorms are no joke. They have a life and an energy all to their own. It is easy for the uniformed to say “Well, the thunderstorm is only ‘Over there’, so why don’t you just avoid it?”. That’s all well and good, but by how much? The best practices say can lead you to avoid a thunderstorm by 20, or more miles. The guidance that I received at my former airline was to avoid them, especially downwind and at altitude, by one mile for every knot of wind that you’re seeing. Hail can be thrown out the top of a thunderstorm and taken downwind many, many miles from the thunderstorm.

And that brings up how you see the thunderstorm. There are limitations to aircraft radars. Aircraft radars reflect well off of water and moisture in the air, but once that moisture freezes, they don’t see it very well.

I have 2 preliminary comments.

1. They flew either through or over a thunderstorm cell. This is very dangerous.
2. If you’re in turbulence that is causing the aircraft to climb and descend “700, 600 feet”, you are not in moderate turbulence. If you’re not holding altitude, you’re in severe turbulence.

The definition of the various levels of turbulence is not subjective. I’ve attached an image from the Airway Manual on turbulence.