"The aircraft pitched up steeply and decelerated from cruise speed to a virtual standstill in the first 30 seconds or so, then went from about 80 mph up to over 100 mph down. None of that would have been interpreted as normal horizontal flight."
There is some confusion among posters here, and in the press, about the flight path. The pitch attitude is reported to be around 15-16 degrees nose up, and the angle of attack to be 35-40 degrees. This translates to a flight path angle of -20 to -25 degrees. If the vertical speed is around 10,000 fpm (~100 knots), then the slant speed has to be the vertical speed divided by the sine of the descent angle, or somewhere around 250 knots. This is the true airspeed. The airplane was not fluttering down vertically like a leaf, and its foward speed was not 60 knots or 107 knots or whatever. As the flight track graphic in the interim report (vertical dimension exaggerated) shows, it was in a stalled glide with a comparatively moderate angle of descent and a good deal of forward speed.