In the two years before the September 11, 2001 attacks, the North American Aerospace Defense Command (NORAD) conducted exercises simulating what the White House says was unimaginable at the time; hijacked airliners used as weapons to crash into targets and cause mass casualties. "One of the imagined targets was the World Trade Center." 'According to an e-mail obtained by the Project On Government Oversight (POGO), members of the U.S. military responsible for defending America's airspace were in fact concerned that a terrorist group would "hijack a commercial airline [sic](foreign carrier)and fly it into the Pentagon." Download copies of USA Today article, POGO Press Release of April 13, 2004, POGO letter to 9/11 commission chairman Kean on April 14, 2004 and a link to an internal NORAD e-mail in PDF format.