The skyscrapers were brought down by the structural damage and fires caused by the impact of hijacked 767 passenger jets crashing 16 minutes apart.
The insurers are collectively responsible for a maximum of $1.1 billion insurance per occurrence. The issue before the court was whether the insurers were obligated to pay for one occurrence or two.
If the verdict is upheld it means the insurers would be obligated to pay up to $2.2 billion to Silverstein, which he would devote to construction at Ground Zero.
A trial that ended in May resulted in an unfavorable result for Silverstein.
Then, a jury decided that 10 of 13 other insurers sued were bound by insurance policies that more narrowly defined "an occurrence."
In those policies insurers could treat the terror attack on the Trade Center as a single occurrence.
Those 10 firms are responsible for a combined payout exceeding $2 billion. The three other firms from that trial were grouped with six insurers in the second trial.
In the next phase of the litigation, a three-person court-appointed panel will evaluate the Trade Center property loss.
Silverstein signed a 99-year lease taking control of the Trade Center in July 2001, six weeks before the attacks that killed 2,749 people and toppled 10 million square feet of commercial space in the twin towers and five other buildings.
His insurance policies were not finalized at the time, leading to the legal disputes over which "per occurrence" policies applied.
The government agency overseeing rebuilding on the 16-acre site, the Lower Manhattan Development Corporation, has tapped Silverstein to develop Freedom Tower.
The Freedom Tower will have 2 million square feet and reach 1,776 feet to become the world's tallest skyscraper when completed in 2009. Its cornerstone was laid July 4.
