The two competing engineering reports released publicly last week are being touted as supporting the respective positions of both sides in the multibillion-dollar WTC insurance litigation.

Both findings were provided earlier to the National Institute of Standards and Technology, a federal agency determining whether any building safety lessons can be learned from the Sept. 11, 2001, destruction of the WTC.

The reports are viewed as evidence in the lawsuit initiated a year ago by a unit of Swiss Re in U.S. District Court in Manhattan.

If the lawsuit survives summary judgment motions and makes it through trial, the ultimate damages award could turn on which side's engineering reports the jury believes.

The declaratory judgment action asks the court to determine whether the collapse of the Twin Towers after terrorists dove jet airliners into the structures constituted one insurable loss or two. If Swiss Re and the other WTC insurers prevail, they would be on the hook for about $3.5 billion, not the $7 billion sought by real estate mogul Larry A. Silverstein and his fellow WTC leaseholders.

The Silverstein parties say their reports establish that the collapse of each of the Twin Towers "was separately initiated" by the impact of an airplane and the resulting fires on the floors that were struck. They also claim that the reports show that the collapse of Tower Two did not contribute to or cause the subsequent collapse of Tower One.

A spokesman for Mr. Silverstein, Gerald McKelvey, executive vice president of Rubenstein Associates Inc. in New York, said the engineering reports show that "the buildings were independent of each other, and if only one was rammed by an airplane, the other one would have withstood ?collapsing damage."

In contrast, James Gamble, an attorney in the New York office of Simpson Thatcher & Bartlett, counsel to Swiss Re, stated that the insurers' engineering reports indicate that the WTC complex was even more highly integrated complex than expected.

He said the report also established that the collapse of one tower would have seriously compromised the viability of the other tower as well as the rest of the complex.

However, Mr. Gamble believes that the engineering reports will be relevant in the litigation only if and when the Silverstein parties prevail on various issues and the litigation reaches the issue of money damages.

At that stage, he explained, the question would be how to allocate the damages between the two occurrences--first-plane impact and second-plane impact.

In a separate development, District Court Judge John S. Martin Jr., the trial judge in the declaratory judgment action, has granted the Silverstein parties and WTC owner Port Authority of New York and New Jersey permission to appeal his June ruling on a summary judgment motion.

In that ruling, the judge declined to rule whether there had been one or two insurable occurrences because he found that the term "occurrence" was ambiguous under an insurance policy issued by Travelers Indemnity.

The Silverstein parties have announced that they will take their appeal to the Second Circuit, which would have the option of declining to hear the appeal.