United States government operations and exercises on September 11 , 2001 On September 11 , 2001 , the North American Aerospace Defense Command ( NORAD ) was involved in an ongoing operation which involved deploying fighter aircraft to northwestern North America . The US Military and NORAD had also planned to conduct several military exercises and a drill was being held by the National Reconnaissance Office , a Department of Defense agency . The operations , exercises and drills were all canceled following the September 11 attacks . Ongoing military operations . " Operation Northern Vigilance " , was a NORAD operation which involved deploying fighter aircraft to locations in Alaska and Northern Canada . The operation was a response to a Russian exercise , in which long - range bombers were dispatched to Russia ' s high north . The operation was one part simulation , one part real world . It was immediately called off after NORAD received word from NEADS that the Federal Aviation Administration had evidence of a hijacking . All simulated information ( so called " injects " ) were purged from computer screens at NORAD headquarters in Colorado . On receiving news of the attacks , the Russians promptly canceled their exercise as well . Planned military exercises . The military exercises ( war games ) planned for September 11 , 2001 included : National Reconnaissance Office drill . Aside from military exercises , a National Reconnaissance Office drill was being conducted on September 11 , 2001 . In a simulated event , a small aircraft would crash into one of the towers of the agency ' s headquarters after experiencing a mechanical failure . The NRO is the branch of the Department of Defense in charge of spy satellites . According to its spokesman Art Haubold : " No actual plane was to be involved - - to simulate the damage from the crash , some stairwells and exits were to be closed off , forcing employees to find other ways to evacuate the building . " He further explained : " It was just an incredible coincidence that this happened to involve an aircraft crashing into our facility , as soon as the real world events began , we canceled the exercise . " Most of the agency ' s personnel were sent home after the attacks . " Operation Tripod " bioterrorism exercise . On September 12 , 2001 , there was due to take place the second part of an exercise known as " Operation Tripod " , set up to " test the plan to distribute antibiotics to the entire city population during a bioterrorism attack " Richard Sheirer , director of the New York City mayor ' s Office of Emergency Management ( OEM ) , had hired " over 1 , 000 Police Academy cadets and Fire Department trainees to play terrified civilians afflicted with various medical conditions , allergies , and panic attacks . " Various individuals were invited to watch , including Mayor Rudolph Giuliani , the police and fire commissioners , and representatives of the FBI and the Federal Emergency Management Agency ( FEMA ) . Pier 92 was set up as a model distribution station where the " victims " of the mock attack who needed to receive antibiotics would be treated . The exercise was a follow - up to a previous training exercise in New York , called " RED Ex " , which took place on May 21 , 2001 . According to the MTI Report " Saving City Lifelines : Lessons Learned in the 9 - 11 Terrorist Attacks " , " September 11 was going to be a busy day at the OEM . Staff members arrived early to prepare for Operation Tripod . " When the September 11 , 2001 attacks began , Operation Tripod was immediately canceled as attentions turned to the real ongoing emergency . Because Pier 92 had been set up ready for the exercise , OEM staff were able to move there and quickly convert it into a large emergency operations center when their original command center ( in WTC Building 7 ) was evacuated and later destroyed . Thus , within 31 hours of the attacks , OEM had a functional facility able to manage the search and rescue effort , just four miles north - northwest of the WTC site . The exercise was later rescheduled and took place on May 22 , 2002 .