Could there be a good possibility that the airplane may have gone down intact. I suggest this on the thus far slow or lack of discovery of a debris footprint. Had the airplane failed at altitude, given the altitude, speed, and winds aloft, then one could reasonably expect an extended area of debris which would track with the airplane as it descended. It would therefore be quite large, and I doubt it would have been difficult to locate.
To compare, I recall all too well the Lockerbie situation with the inflight breakup of PA and the area that was affected. The heavy portion fell in the village, and nearby area, but countless other items extended for miles. Some large, some small.
On the other hand, MS990 created only two relatively small debris field in the Atlantic. One 62 X 66 meters, and the other 83 X 73. This airplane entered the water mostly intact. Radar coverage made it quickly discovered.