The World Trade Center leaseholder has won a court victory over his insurers as he attempts to rebuild the site.
Mr Silverstein wants to restore 10 million sq ft of office space
A New York jury has decided that the 11 September 2001 attack on the two towers constituted two separate events.
The US District Court ruling means Larry Silverstein could now get an extra $1.1bn (£0.56bn) from nine insurers to finance reconstruction.
He has been fighting the insurance companies, arguing he was owed $7bn (£3.6bn) - double his $3.5bn policy.
The firms had argued at the District Court for the Southern District of New York that the twin strikes on the trade centre were part of a single, continuous, planned attack.
Mr Silverstein said in a statement that he was "thrilled" with his victory.
"The decision means an additional billion dollars of insurance proceeds will be available, which, together with Liberty Bonds, will ensure a timely and complete rebuild of the World Trade Center," he said.
"I strongly felt, and the jury agreed, that the destruction of the twin towers by two separate airplanes at two separate times was two separate occurrences and that these insurers have an obligation to pay their fair share
to help make Lower Manhattan whole again."
He lost a similar case earlier this year against a dozen other firms. A different jury ruled policies from those firms had defined such an attack as a single event.
That insurance document tightly defined "occurrence" to make it clear that the 11 September attack in New York was one insurable event.
The defendants then included Swiss Re, which is liable for a single payout of up to $880m. A third trial with a different jury might be held to determine how much Swiss Re will pay.
After the latest decision one of the insurers, Allianz AG, said it was "disappointed" and pledged it would appeal against the verdict if necessary.
A spokesman said Allianz would "pursue all our legal remedies".
Mr Silverstein wants to restore 10 million square feet
(900,000 square metres) of office space on what has become known as Ground Zero.