The North American Aerospace Defense Command (NORAD) conducts an exercise, called Vigilant Virgo 99-1, in which simulated missiles are injected into its radar systems, apparently similar to the way simulated information will be injected onto its radar screens for a training exercise on the morning of September 11, 2001. [US Department of Defense, 1/15/1999; Toronto Star, 12/9/2001; Arkin, 2005, pp. 546] In August 1998, Secretary of Defense William Cohen directed the commanders in chief who are responsible for the Department of Defense’s unified combatant commands to plan, carry out, and report on a series of simulated Year 2000 “operational evaluations.” [United States General Accounting Office, 6/1999, pp. 8 
; United States General Accounting Office, 11/1999, pp. 15 ] Vigilant Virgo is the first in a series of NORAD operational evaluations that are going to be held in response to this order. [US Department of Defense, 1/15/1999; United States General Accounting Office, 6/1999, pp. 2 ; Military Operations Research Society, 6/22/1999, pp. 193 ]
Exercise Tests NORAD’s Year 2000 Preparedness – The three-day exercise is intended to evaluate if NORAD’s systems are vulnerable to the Year 2000 (Y2K) computer problem, which would be caused by computers being unable to properly read dates at the start of the new millennium. [US Department of Defense, 1/15/1999; New York Times, 2/9/1999] It evaluates the capability of NORAD’s systems to track and forward information about missile and space air threats when the command’s clocks are rolled forward to January 1, 2000. [United States General Accounting Office, 6/1999, pp. 8-9 ] The exercise is a collaborative effort in which NORAD is supported by personnel, equipment, and facilities belonging to the US Space Command and the US Strategic Command. [US Department of Defense, 1/14/1999; US Department of Defense, 1/15/1999]
‘Missile Events’ Are Injected into NORAD’s Sensors – Vigilant Virgo focuses on the missile warning element of NORAD’s integrated tactical warning and attack assessment function. [United States General Accounting Office, 6/1999, pp. 11 ; Military Operations Research Society, 6/22/1999, pp. 193 ] It involves “well over 30 missile events” being “injected” into NORAD’s sensors, according to Lieutenant Colonel Warren Patterson, a member of the Joint Staff Year 2000 Task Force. These simulated events involve data that is injected “as though it [is] being sensed for the first time by a radar site,” Deputy Secretary of Defense John Hamre will later describe. Some of the simulations involve mass attacks, while others involve attacks by a single missile. [US Department of Defense, 1/15/1999] The Y2K preparedness of the entire ground radar array network is analyzed during the exercise. [Bulletin of the Atomic Scientists, 3/1999]
Exercise Finds No Vulnerabilities in NORAD’s Systems – Vigilant Virgo will be considered a success. The exercise will find that there is “no degradation in any of the systems, whether they were in the Year 2000 environment, the virtual Year 2000 environment, or whether they were in the real world, 1998 environment,” Patterson will say. “We are highly confident now, at this point, that CINC [commander in chief] NORAD can do his early warning mission,” he will conclude. [US Department of Defense, 1/15/1999]
Exercise on 9/11 Will Use Simulated Radar Information – NORAD is the military organization responsible for monitoring and defending North American airspace. [9/11 Commission, 7/24/2004, pp. 16; Department of National Defence, 7/25/2017] Personnel at its Northeast Air Defense Sector (NEADS), based in Rome, New York, will be responsible for coordinating the military’s response to the 9/11 hijackings. [Shenon, 2008, pp. 203] It will be conducting an exercise on the morning of September 11, 2001, which, like Vigilant Virgo, involves simulated information being injected onto its radar screens (see (9:00 a.m.) September 11, 2001, 9:34 a.m. September 11, 2001, and 10:12 a.m. September 11, 2001). [Toronto Star, 12/9/2001] NORAD will conduct a follow-on exercise to Vigilant Virgo from February 15 to February 28, 1999, called Amalgam Virgo 99-2, which will involve a comprehensive evaluation of its systems for aerospace control, air warning, missile warning, and space warning. [United States General Accounting Office, 6/1999, pp. 11 ; Arkin, 2005, pp. 253-254] Whether that exercise will involve simulated information being injected onto radar screens is unclear.
9:34 a.m. September 11, 2001: NEADS Surveillance Technicians Instructed to Remove Simulated Information from Radar Screens
A technician at NORAD’s Northeast Air Defense Sector (NEADS) instructs personnel on the NEADS operations floor to turn off their “sim switches,” apparently so as to remove from their radar screens simulated information for a training exercise that was being conducted this morning. [Northeast Air Defense Sector, 8/23/2001; North American Aerospace Defense Command, 9/11/2001; 9/11 Commission, 2004]
Staffer Complained, ‘Let’s Get Rid of This Goddamn Sim’ – A few minutes earlier, at 9:30 a.m., a member of staff on the operations floor complained about simulated information—presumably false tracks—appearing on NEADS radar screens. He said: “You know what, let’s get rid of this godd_mn sim. Turn your sim switches off. Let’s get rid of that crap.” [North American Aerospace Defense Command, 9/11/2001; North American Aerospace Defense Command, 9/11/2001] (A “sim switch” presumably allows simulated material on radar scopes to be turned on or off.)
Technician Instructs, ‘Turn Off Your Sim Switches’ – Now a member of NEADS staff, who according to a 9/11 Commission document is Technical Sergeant Jeffrey Richmond, gives an instruction to the NEADS surveillance technicians, “All surveillance, turn off your sim switches.” Seconds later, apparently in response to this instruction, someone on the operations floor tells a colleague, “You got your sim switches down.” [North American Aerospace Defense Command, 9/11/2001; 9/11 Commission, 2004]
Sim Switches Turned On for Day’s Exercise – Simulated material (“sim”) is apparently appearing on NEADS radar screens because of the NORAD training exercise, Vigilant Guardian, that was being conducted this morning (see (6:30 a.m.) September 11, 2001). Former Deputy Secretary of Defense John Hamre has revealed that NORAD has the capacity to inject simulated material into the system, “as though it was being sensed for the first time by a radar site.” In a training exercise in December 1998, for example, NORAD ran “30 different simulations, some of them being mass attacks, some of them being single missiles.” An information page on the current exercise stated, “All of NEADS, operations personnel are to have their sim switches turned ‘on’ starting at 1400Z 6 Sept. 01 till endex [the end date of the exercise].” Since Vigilant Guardian was originally scheduled to continue until September 13, this would mean NEADS personnel had their sim switches turned on this morning. [US Department of Defense, 1/15/1999; Northeast Air Defense Sector, 8/23/2001]
Radar Equipment Set to Display ‘Sim Tracks’ – A memo outlining special instructions for Vigilant Guardian participants further detailed how NORAD equipment needed to be set to display simulated material during the exercise. It stated: “The exercise will be conducted sim over live on the air sovereignty string. The Q-93 must be placed in the mixed mode to allow the telling [i.e. the communicating of information between facilities] of sim tracks.” [Northeast Air Defense Sector, 8/23/2001] The Q-93 is a piece of equipment used by NORAD, which is described as “a suite of computers and peripheral equipment configured to receive plot data from ground radar systems,” and which “performs track processing.” [General Accounting Office, 12/24/1992 ; Federation of American Scientists, 4/23/2000] The Q-93 also “receives flight plans from the FAA, and has bi-directional communications with NORAD headquarters and a real-time link to AWACS [Airborne Warning and Control System planes].” [Satterthwaite, Corman, and Herm, 6/2002]
Exercise Supposedly Canceled Earlier On – While NEADS radar scopes are still displaying simulated material as late as 9:34 a.m., some accounts will claim the Vigilant Guardian exercise was canceled shortly after 9:03 a.m., when the second World Trade Center tower was hit (see (Shortly After 9:03 a.m.) September 11, 2001). [Airman, 3/2002; Filson, 2003, pp. 59] And according to a report in the Toronto Star, “Any simulated information” for the exercise was “purged from the [radar] screens” at NORAD’s operations center in Cheyenne Mountain, Colorado, shortly before the second WTC tower was hit (see (9:00 a.m.) September 11, 2001). [Toronto Star, 12/9/2001] However, NEADS will receive a phone call from the operations center at 10:12 a.m. in which the caller asks it to “terminate all exercise inputs coming into Cheyenne Mountain” (see 10:12 a.m. September 11, 2001). [North American Aerospace Defense Command, 9/11/2001]
