Months after losing his first bid to have the attacks of September 11 2001 on the World Trade Centre declared two separate events, leaseholder Larry Silverstein has won his latest court battle with insurers.

A jury decision in a New York court hearing his claim against several insurers doubles to $US2.2 billion the amount Mr Silverstein can claim. In addition to rebuilding the towers, he must continue paying rent of $US109 million a year to the Port Authority.

The insurers affected by this case represent $US1.13 billion of the centre’s insurance program. Another 15 syndicates represent the remaining $US2.42 billion of cover.

Mr Silverstein lost the first trial regarding insurance payouts earlier this year, but this new decision means the developer could ultimately collect up to $US4.6 billion.

His lawyers argued that the two aircraft striking each of the centre’s towers constituted separate direct and physical losses.

The insurers with the largest exposure in the case are Swiss Re, Allianz, Industrial Risk Insurers, Travelers Indemnity and Royal Specialty.

UK insurer Royal & Sun Alliance says it is too early to assess the effect of the decision on its balance sheet. Allianz – which may have to pay up to $US45.7 million – says the decision won’t affect its financial results.

Some insurers have already criticised the decision, saying they intended the terms of their involvement to mirror those in a policy form used during the placement process by Mr Silverstein’s broker, Willis Group. The form, known as Wilprop, had been used to treat the attacks as one occurrence.

Appeals are likely.