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FILE - In this Sept. 11, 2001 file photo, smoke, flames and debris erupt from one of the World Trade Center towers after a plane strikes it, in New York. The first tower was already burning following a similar attack minutes earlier. Osama bin Laden, the glowering mastermind behind the Sept. 11, 2001, terror attacks that killed thousands of Americans, was slain in his luxury hideout in Pakistan early Monday, May 2, 2011 in a firefight with U.S. forces, ending a manhunt that spanned a frustrating decade. (AP Photo/Chao Soi Cheong, File) MANDATORY CREDIT

FILE - In this Sept. 11, 2001 file photo, smoke, flames and debris erupt from one of the World Trade Center towers after a plane strikes it, in New York. The first tower was already burning following a similar attack minutes earlier. Osama bin Laden, the glowering mastermind behind the Sept. 11, 2001, terror attacks that killed thousands of Americans, was slain in his luxury hideout in Pakistan early Monday, May 2, 2011 in a firefight with U.S. forces, ending a manhunt that spanned a frustrating decade.

World Trade Center attack

World Trade Center terrorist attack