The Utah Construction workers blasting and building underground may not have guessed how frequently NORAD would be depicted in feature films as the country's watchdog against nuclear attack. For decades NORAD acted as a weather center, as well as a defensive intelligence base with ground-based radar, airborne satellites, fighter aircraft, and command facilities. Sometime during the 1990s a NORAD sector performed a drill responding to a plane flying into a tall tower. That nightmare scenario became true on September 11, 2001, when commercial airliners hijacked by terrorists struck the World Trade Towers and the Pentagon. A fourth plane, which apparently targeted the White House or the Capitol, crashed in Pennsylvania. Immediately following the attacks, NORAD directed the nation's fighter aircraft in providing combat air patrols over Manhattan, Washington DC, and most major cities in the United States. The number of alert bases with fighter planes increased from seven around the nation's perimeter to 26 overall.