WASHINGTON (CNN) -- A comment Defense Secretary Donald Rumsfeld made during a Christmas Eve address to U.S. troops in Baghdad has sparked new conspiracy theories about the terrorist attacks of September 11, 2001. In the speech, Rumsfeld made a passing reference to United Airlines Flight 93, which crashed in Pennsylvania after passengers attempted to stop al Qaeda hijackers. But in his remarks, Rumsfeld referred to the "the people who attacked the United States in New York, shot down the plane over Pennsylvania." A Pentagon spokesman insisted that Rumsfeld simply misspoke, but Internet conspiracy theorists seized on the reference to the...