NEW YORK (Reuters) – A federal judge is days away from decidingif New York developer Larry Silverstein can recover as much as$3.5 billion from airlines for damages to the World TradeCenter on Sept. 11, 2001, on top of more than $4 billion hehas received from insurers.

U.S. District Judge Alvin Hellerstein started athree-day trial on Monday in which he will decide how much of theinsurance payments should offset the damages Silverstein is seekingfrom the airlines. These include United Airlines, now UnitedContinental Holdings Inc, American Airlines and American'sparent, AMR Corp.

Roger Podesta, a lawyer for the airlines, argued thatSilverstein's insurers have already paid him for the same losses heis seeking from the airlines.

The insurance payments and the claims against the airlines are“for the same category of loss,” Podesta said in opening argumentsin a packed courtroom in federal court in New York.

But Rich Williamson, a lawyer representingSilverstein's World Trade Center Properties, said theairlines' argument “defies reality.”

“The grocer would not say 'the categories of food that I sellare food,'” Williamson said. “You can't just say, 'I have economicloss.'”

Hellerstein is deciding the case without a jury. He said in apre-trial hearing that he expects to rule immediately followingclosing arguments, scheduled for Wednesday.

Should Hellerstein decide the claims do not correspond with eachother, Silverstein would then have to prove liability in a separatetrial.

Hellerstein, a Bronx native and U.S. Army veteran nominated tothe bench by President Bill Clinton, has presided over asprawling portfolio of 9/11-related cases.

In January, Hellerstein will hear a trial pitting CantorFitzgerald, which lost 658 employees in the attacks, againstAmerican Airlines. The financial services firm sued the airlineover lost business and the destruction of its offices inthe World Trade Center.

United Airlines merged with Continental Airlines in 2010 toform United Continental Holdings.AMR Corp, whichfiled for bankruptcy in 2011, has announced plans to mergewith US AirwaysGroup Inc.

The cases are World Trade Center Properties LLC, et al.v. United Airlines Inc; World Trade Center Properties LLC, etal. V. American Airlines Inc, et al, v. American Airlines Inc etall, U.S. District Court, Southern District of New York,Nos 08-3719 and 08-3722.