"Swiss Re is going to prove its case out of the mouths of Silverstein's own representative," said the insurer's lawyer, Barry Ostrager, at the World Trade Center trial in Manhattan.
At the beginning of the trial, which is expected to last between six and eight weeks, Judge Michael Mukasey cautioned jurors to focus solely on the question of insurance.
The insurers, led by Swiss Re, have argued that the cover in place at the time of the attacks defined the towers' destruction as a single event.
World Trade Center developer Larry Silverstein has argued that a different insurance binder was in force, allowing the events of 11 September to be defined as two separate attacks.
Silverstein's lawyer, Herbert Wachtell, accused the insurers of "trying to rewrite history".
Setting out his case, Wachtell described the attacks as "two planes, two hits on two separate towers, two explosions, and two fires in two towers".