Joint service troops stand ready to unveil the Pentagon Memorial as the U.S. Air Force Band plays "Who Are the Braveî on Sept. 11, 2008. The national memorial is the first to be dedicated to those killed at the Pentagon on Sept. 11, 2001. The site contains 184 inscribed memorial units honoring the 59 people aboard American Airlines Flight 77 and the 125 in the building who lost their lives that day.