This could have been wind shear: i.e. the plane was flying into a strong headwind and then suddenly found itself in a tailwind. This is what caused the Delta crash at D/FW back in the 80's.
However, the Delta plane was on final approach to the airport near the ground. This plane was presumably at high altitude and cruise speed, although they may have slowed to "maneuvering speed" because they expected heavy turbulence.
The "flying too slow" may have been an erroneous measurement, or it may have have been when the plane first went out of control.
One wonders why you would post when you obviously know nothing about what you are talking about. Posts like this would make me question EVERYTHING YOU EVER POST.
Wind shear is a problem when you are low and slow. (I.e. takeoff and landing.) It is not a problem when you are high and relatively fast. When you are low and slow you might be only 20 knots above the stalling speed (that speed at which the wings no longer generate sufficient lift to keep the plane aloft). So a sudden loss of 30 knots due to wind shear would cause the plane to begin falling. (NB Falling and descending mean different things. I said falling.) When you fall close to the ground bad things happen.
At 35,000 feet (or whatever) the situation is somewhat different. Usually you have much a much greater speed margin over the stall speed. But even if you do stall, you just fall. In all but the most unusual circumstances, the fall increases the speed of the air over the wings and lift returns. Even if this takes several thousand feet, there is no ground anywhere near enough to cause a problem. I really don't know how much altitude the big boys would be likely to lose during a stall recovery but my recollection is that someone just learning to fly a single engine plane (which I did over 30 years ago) is expected to be able to recover from a stall without losing more than 100 feet of altitude.
ML/NJ