Silverstein Properties Inc., along with the Port Authority and other insureds, has filed two briefs with the United States Court of Appeals for the Second Circuit establishing that the attacks on the World Trade Center constitute two occurrences for purposes of the $3.55 billion "per occurrence" insurance coverage of the Twin Towers, and that the lower court erred in ruling that three of the 24 insurers of the World Trade Center could limit their payments to a single occurrence.

If there are two occurrences, Silverstein and its co-insureds will reportedly be able to recover up to $6.7 billion for use in rebuilding; if there is one occurrence, recovery would be limited to $3.55 billion, an amount substantially less than the anticipated cost of rebuilding the World Trade Center site.