Given it took a month to search 850 km2 (possibly with some deep areas missed), the proposal to search 60,000 km2 suggests a different methodology. Perhaps using multiple more capable AUVs.
Anyway the dramatic increased size of the proposed area suggests we are really back to the Inmarsat arcs.
I guess a ditching is an advantage here. We will presumably be looking for a large relatively intact fuselage rather than a debris field.