A significant number of apparent terrorist incidents occurred on September 11, 2001, in which President Bush or locations associated with him, like the White House and Camp David, seemed to be the target. And yet for all these incidents, the apparent threat was subsequently claimed to be unfounded, perhaps having come about due to a misunderstanding. A possibility that has remained unexamined, however, is that the incidents were in fact scenarios in training exercises taking place that day.
It seems reasonable to assume that if the incidents were indeed exercise scenarios, the Secret Service, as the agency responsible for protecting the president and the White House, would have been participating in them. Alarmingly, though, the times at which some of the incidents occurred indicates that if they were scenarios in training exercises, these exercises were not canceled in response to the attacks on the World Trade Center and the Pentagon, but instead continued until well after the real-world crisis ended. If the Secret Service was indeed involved in exercises at the time of the 9/11 attacks, then, we surely need to consider what effect these exercises had on the agency's ability to respond to the attacks.
Below are descriptions of eight apparent terrorist incidents that occurred around the time of the 9/11 attacks, in which the president or a location associated with the president appeared to be the target. The first two incidents involved the president himself seeming to be the terrorists' target; the next three involved Air Force One, the president's plane, being the apparent target; and the final incidents involved the places where President Bush lived, such as the White House, being the apparent target.
New 9/11 Timeline Entries: Hijacking Exercises, Air Force One's Movements, Laura Bush on Sept. 11, and More
From the History Commons Groups blog:
A large number of entries have been added to the Complete 9/11 Timeline at History Commons, most off which provide new details about the events of the day of September 11, 2001.
One new timeline entry describes a training exercise based on the scenario of a possible terrorist attack that was run on the morning of September 11 by the US Coast Guard in Tampa Bay, Florida, quite close to Sarasota, where the president was at the time. Another entry deals with a meeting scheduled to take place at the Pentagon that morning, regarding a planned "disaster exercise" at the nearby Navy Annex building.
An entry reveals that a number of FBI agents had, for reasons that are unknown, already arrived at the Navy Annex when the Pentagon was hit. Later on, the Navy set up a new command center at the Navy Annex, after its original command center was destroyed in the Pentagon attack.
Several entries describe the futile attempts of intelligence officers at NORAD's Northeast Air Defense Sector (NEADS) to obtain information about the first hijacking. After learning of the hijacking, a NEADS intelligence officer called the FBI's Strategic Information and Operations Center and the National Military Joint Intelligence Center at the Pentagon, but neither of them could provide any information. Searches on the SIPRNET--the US military Internet system--also revealed nothing. Furthermore, the threat briefing at NEADS that morning had included no indication of an increase in the terrorist threat level.
Some NEADS personnel have said they were monitoring Flight 93 long before the time at which the 9/11 Commission concluded the military was first alerted to this hijacked aircraft. Also, a commander at NEADS complained that an officer from the NEADS battle cab had come down to the operations floor, where he had been "circumventing my system." What is more, NEADS personnel only learned that the president's plane, Air Force One, was airborne about half an hour after it took off from Sarasota.
- Major James Fox, Northeast Air Defense Sector, September 11, 2001
Key military personnel who were responsible for protecting the U.S. against the 9/11 attacks may have been seriously hindered in their ability to respond because of a large-scale air defense exercise they were participating in when the attacks occurred. Evidence indicates that the personnel, whose responsibilities included ordering fighter jets into the air to intercept the hijacked planes, were unclear about what was "real-world" and what was "exercise." They may have been led to believe that the terrorist attacks were just simulated scenarios.
These individuals worked at the Northeast Air Defense Sector (NEADS) in Rome, New York. Audio recordings of the operations floor at NEADS reveal staffers suggesting that the catastrophic events of September 11, 2001 could have been part of the exercise. They sometimes even made jokes and laughed about what was taking place, further indicating that they were mistaking actual events for exercise simulations. Even senior commanding officers have admitted wondering if the terrorist attacks were part of the exercise.
And while staffers sometimes apparently made clear that an event was unconnected to the exercise by referring to it as being "real-world," there is evidence that the term "real-world" may in fact be a way to describe live events played out within an exercise, perhaps involving real aircraft getting airborne, rather than just hypothetical scenarios.
Furthermore, NEADS personnel previously participated in exercises that included scenarios resembling the 9/11 attacks, such as plane hijackings and aircraft being crashed into skyscrapers in New York, and this could have increased the likelihood that they would mistake the events of September 11 for exercise simulations.
Although much remains speculative, the available evidence raises serious questions about whether the exercise at NEADS on September 11 was a deliberate tactic used to hinder skilled and dedicated professionals, thereby preventing them from stopping the terrorist attacks.
New 9/11 Timeline Entries: Fighters on Training Mission, Special Ops Exercise, Intercepts over the Atlantic, and More
From the History Commons Groups blog:
Entries have been added to the Complete 9/11 Timeline at History Commons, which, in particular, reveal new details about events from the day of September 11.
Several entries describe how a group of fighter jets from Otis Air National Guard Base in Massachusetts were taking part in a training mission when the terrorist attacks began. Although the pilots of these jets had seen two other fighters taking off from their base in response to the hijacked Flight 11, they were unaware of the reason for the scramble. They therefore continued with their training mission--described as a "mock war scenario"--over the Atlantic Ocean.
The fighters were recalled to Otis Air Base after the base started preparing all of its fighters for takeoff. At least one of the pilots involved in the training mission soon took off again. Along with another pilot, his first task was to intercept a military cargo plane over the Atlantic. The two fighters were subsequently sent to New York, where they helped patrol the airspace over the city. Before returning to their base, they were directed to inspect a supposedly suspicious aircraft that turned out to be just a tanker plane that had been providing them with fuel.
Military personnel were also concerned about a convoy of aircraft approaching America across the Atlantic, which repeatedly failed to respond to radio communications. But when fighters intercepted the convoy, they found it was just some military planes coming back from Europe.
While September 11, 2001 is well known as the day when the U.S. suffered its worst terrorist attack, what is little known is that it was also a day when large sections of the armed forces around the nation had been preparing to fight a simulated nuclear war, as part of major training exercises being conducted at the time. In their annual exercises "Vigilant Guardian" and "Global Guardian," the North American Aerospace Defense Command (NORAD) and the United States Strategic Command (Stratcom) were scheduled to carry out what has been described as a "simulated air war," a "full-blown nuclear war" exercise, a "fictional nuclear war," and a "practice Armageddon."
No official attempts have been made to fully investigate these exercises and what effect they had on the military's response to the 9/11 attacks. But evidence indicates they caused at least some confusion over what was "real-world" and what was simulation, and they may also have been a factor behind the communication problems experienced by military personnel that day. Other evidence suggests that some actions that have been presented as reactions to the terrorist attacks may actually have been related to these exercises--actions such as raising the alert status of American armed services to Defcon 3 and closing the huge "blast doors" to NORAD's operations center in Cheyenne Mountain, Colorado. There is also evidence that other "practice Armageddon" exercises were being conducted at the time of the 9/11 attacks, but details of these are unknown.
AMERICA'S AIR DEFENDERS WERE SET TO FIGHT A 'SIMULATED AIR WAR' ON SEPTEMBER 11
Perhaps the most important exercise to consider is NORAD's exercise called "Vigilant Guardian." Close examination of this exercise is imperative due to the crucial role NORAD had to play in responding to the 9/11 attacks.
From the History Commons Groups blog:
A large number of new entries have been added to the Complete 9/11 Timeline at History Commons describing important events that took place on the day of 9/11, while other new entries add to the growing body of information about 9/11-related training exercises.
One new entry describes how, from 1998, the US Secret Service included computer simulations of planes crashing into the White House in its training exercises. Another notable exercise was held early on the morning of September 11 in the White House Situation Room, based on the scenario of a terrorist bombing in the Middle East.
Despite claims by the U.S. government that the events of 9/11 were unexpected, from 1998 the Secret Service was "crashing planes into the White House ... on a simulation program provided by the military" during training exercises, according to a retired Secret Service agent who had been involved with running those simulations. When this individual and his Secret Service colleagues learned that a plane had crashed into the World Trade Center on the morning of September 11, 2001, one of those colleagues pointed to him and commented, "You know all about that." 
The existence of these plane crash simulations was revealed by Paul Nenninger, who worked for the Secret Service for 26 years, in a chapter he wrote for a book published in 2005. In 1997, Nenninger had been assigned to the Secret Service's James J. Rowley Training Center, just outside Washington, DC, in Beltsville, Maryland, where he served as program manager in charge of the Security and Incident Modeling Lab (SIMLAB). 
Backup Communications System Was 'Miraculously' Switched on for 'Exercise Mode' and Ready for Use on 9/11
A special backup network that allows communications between government and military agencies to continue during emergencies was "miraculously" switched on the day before 9/11, and so was already operational when the terrorist attacks in New York and at the Pentagon took place. The Special Routing Arrangement Service (SRAS) was, for reasons unknown, turned on for "exercise mode" on September 10, 2001, and was therefore ready to be utilized the following day, when there was a national emergency like that for which it was intended.
The SRAS is the responsibility of a little-known government agency called the National Communications System (NCS), which works to keep critical telecommunications functioning during emergencies and played a crucial role in the government's response to the 9/11 attacks, helping to maintain and restore communications networks. Furthermore, the SRAS is related to "Continuity of Government"--a plan that was activated for the first time during the attacks.
'Let's Get Rid of This Goddamn Sim': How NORAD Radar Screens Displayed False Tracks All Through the 9/11 Attacks
Military personnel responsible for defending U.S. airspace had false tracks displayed on their radar screens throughout the entire duration of the 9/11 attacks, as part of the simulation for a training exercise being conducted that day. Technicians at NORAD's Northeast Air Defense Sector (NEADS) were still receiving the simulated radar information around the time the third attack, on the Pentagon, took place. Those at NORAD's operations center in Cheyenne Mountain, Colorado, were still receiving it several minutes after United Airlines Flight 93 apparently crashed in rural Pennsylvania.
No one has investigated why false tracks continued being injected onto NORAD radar screens long after the U.S. military was alerted to the real-world crisis taking place that morning. And yet we surely need to know more about these simulated "inputs" and what effect they had on the military's ability to respond to the 9/11 attacks.
NEADS TECHNICIANS TOLD TO TURN OFF 'SIM SWITCHES'
Several hours after the 9/11 attacks in New York and Washington occurred, a passenger aircraft heading to the U.S. from Seoul, South Korea, was mistakenly considered hijacked. In a little-reported series of events, the pilots of Korean Airlines Flight 85 gave numerous indications that their plane had been taken over by hijackers, even though it had not. KAL 85, a Boeing 747 that had been due to land in Anchorage, Alaska, for a refueling stop, was consequently diverted to an airport in Canada. The military launched fighter jets to tail it and, with authorization from the Canadian prime minister, threatened to shoot the plane down if it refused to change course. Only after KAL 85 landed were officials able to confirm that no hijacking had taken place.
While a person might suggest this crisis was just the result of confusion due to the unprecedented events earlier that day, the number of indications the pilots gave that their plane was hijacked, and their repeated failure to confirm that this was not the case, raises another possibility: Could KAL 85 have been playing the part of a hijacked aircraft in a military training exercise?