A federal judge in Manhattan ruled Wednesday that United Airlines was not responsible for the collapse of a third World Trade Center building on Sept. 11, 2001.

The plaintiff in the case, Larry Silverstein, the leaseholder of the World Trade Center property, claimed that the collapse of 7 World Trade Center stemmed from airport security lapses that allowed hijackers to crash an American Airlines plane into the complex.

Judge Alvin K. Hellerstein granted a request by United and its parent, United Continental Holdings, to dismiss Mr. Silverstein’s claims. Tower 7 collapsed several hours after being pierced by debris from the crash of American Airlines Flight 11 into the nearby 1 World Trade Center. Two of the Flight 11 hijackers, Mohammed Atta and Abdulaziz Alomari, began their trip to New York at the Portland International Jetport, in Maine. They boarded a flight to Logan International Airport in Boston, from which they connected to the American Airlines plane.

Mr. Silverstein’s lawyers argued that because United was among the airlines that ran Portland’s only security checkpoint, it was legally responsible for the screening of all passengers and had missed a “clear chance” to prevent the hijacking.