NORAD Cheyenne Mountain Complex in Colorado Springs, CO

COLORADO SPRINGS, CO - MAY 11: At the interior entrance to the Cheyenne Mountain Complex headquarters for NORAD two military personnel exit the administrative area May 11, 2004 in Colorado Springs, Colorado. Constructed during the Cold War period in 1958, NORAD (North American Aerospace Command) was responsible for external air, missile and space defense. Since September 11, 2001, it now watches 7,000 aircraft per day within the US NORAD covers each aircraft's flight pattern including contingencies for the US President's flights and landings. NORAD coordinates with civilian authorities and works with the Pentagon, federal, state and local authorities. Canadian military officials make up 10-15 percent of NORAD's 326 total staff. NORAD works with Department of Homeland Security (DHS) but is not part of DHS. The personnel work at 7,000 feet inside a granite mountain. Two 25-ton security doors seal the inside offices from any type of attack. NORAD has a self sufficient survival system with independent water and air supplies. (Photo by Robert Nickelsberg/Getty Images)