I tend to believe that the debris field would not be as large as one might think. Depending upon what happened to the airplane after making contact with the water, if it did not fail and separate into several parts, while being airborn, then most should rest fairly close together on the bottom. The EgyptAir 990, while structural failure occured at altitude, remained at two relatively small areas. The bulk of the airplane's fuselage, wings, engines, gear, etc footprint was only approximately 70 X 80 meters. Of course, this was in 220 feet of water, quite different from the search now going on. Even so, I would think that the main part of the airplane and large parts would not have drifted that much.
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