The insurance arrangements for the World Trade Center came under renewed scrutiny this week as the second stage of the insurance court battle got underway.

The second phase involves 11 insurers, representing $1.1bn of the $3.55bn insurance cover, who were not bound by the WilProp form, which defined the attacks of September 11 as a single occurrence.

The insurers are now seeking to establish that the forms they were bound by defined the attacks as a single occurrence, limiting their potential payout.

Making their opening statement, lawyers for WTC leaseholder Larry Silverstein argued that the insurance arrangements had listed a number of events that were to be regarded as a single event if they occurred within 72 hours, but the list did not include terrorism.

Bernard Nussbaum, representing Silverstein, said evidence would show that the insurance forms did not specifically define the word occurrence, leaving the insurers open to a double payout.

In response, Harvey Kurzweil, representing Travelers Insurance, said insurers were only allowed to be bound under forms without “material differences” from the WilProp form, meaning that all forms had the same understanding of occurrence as WilProp.