if the plane was flying entirely by auto pilot and then the fuel ran out the auto pilot would likely disengage and expect the pilots to take over. if the pilot were in the cockpit and aware, it is likely that as the plane neared the ocean he would lower the flaps to allow the plane to fly slower to reduce the speed at impact. Lowered flaps help prevent stalls at low air speeds and are deployed while landing. While cruising at altitude they are kept up to reduce drag. If up and attached to the plane at impact they could be expected to be stopped when the wing in front of the stops suddenly from impact with the water. the leading edges and the attachment points will show different bending and stress patterns depending on how the plane crashed.
However, there is another possible scenario. If the plane was flying at high altitude and control was lost. (perhaps due to a stall because of engine flame out) the plane could have gone into a steep uncontrolled dive. This could have subjected the plane to extreme over speed. At very high speeds the plane would break apart. it is not unheard of for airliners to come apart in the air just because of mistakes made by the pilots.
i believe this is a composite part. Made of fiber and glue. Some of the edges in other photographs show what seems to be fraying/delamination on the edges. This could be caused by sea water or it could have been due to over-speed.