President George W. Bush was allowed to continue with a routine visit to a school when the terrorist attacks occurred on September 11, 2001. Remarkably, members of the Secret Service and other personnel responsible for protecting the president failed to evacuate him from the Emma E. Booker Elementary School in Sarasota, Florida, after they learned that a second plane had crashed into the World Trade Center and it became clear that America was under attack.

As the nation's leader, Bush should have been considered a likely target for terrorists. Furthermore, his schedule had been publicized in advance and so terrorists could have found out where he would be on September 11.

From the History Commons Groups blog:

Many entries have been added to the Complete 9/11 Timeline at History Commons, covering various events relating to the 9/11 attacks, including a number of anti-terrorism training exercises held in the years leading up to 9/11 and various incidents from the day of September 11, 2001, itself.

Numerous Exercises Prepared for a Terrorist Attack in New York

Many new timeline entries describe training exercises that were held in New York before 9/11. These include Operation ICE, the city's largest ever terrorism response exercise, which was held in November 1997 and included a simulated chemical attack near the World Trade Center. Another exercise, which tested the response to a biological attack, was held in June 1999 at the city's new emergency command center in World Trade Center Building 7.

Over a million dollars' worth of diamonds and bonds were apparently stolen from an armored truck in the basement of the World Trade Center when the terrorist attacks took place on September 11, 2001, which suggests that someone--or some people--may have had foreknowledge of the 9/11 attacks and exploited the chaos they knew the attacks would generate in order to commit their crime at a time when there was minimal risk of getting caught.

The black boxes from the planes that crashed into the World Trade Center on September 11, 2001, were found and retrieved in the weeks after the 9/11 attacks, a significant amount of evidence indicates. And yet government officials and the official investigation into the attacks have asserted that these devices were never recovered.

A plane's two black boxes record important information about a flight. The black boxes from American Airlines Flight 11 and United Airlines Flight 175--the planes that hit the World Trade Center--could therefore have helped investigators determine what happened on these aircraft before they crashed on September 11.

A number of individuals who worked in key positions apparently knew that the Twin Towers of the World Trade Center were going to collapse before the two buildings came down on September 11, 2001. These men talked with colleagues about their concern that the towers might come down, and some of them issued stark warnings about the danger and ordered people to get away from the World Trade Center.

Although their warnings have, in some cases, been credited with saving lives, the behavior of these men is, on closer examination, surprising and quite suspicious. This is because the general opinion before September 11 was that the Twin Towers would survive being hit by planes and the outcomes of previous high-rise fires should have led the men to think the towers would easily endure the fires they suffered on September 11 without collapsing.

From the History Commons Groups blog:

Many entries have been added to the Complete 9/11 Timeline at History Commons, which describe a variety of events relating to the 9/11 attacks, with numerous entries revealing new details of the events of September 11, 2001.

Training Exercises Were Held in the Run-Up to 9/11

Several new timeline entries describe training exercises that were held in the years and months before 9/11. In May 1998, an exercise was held at the Pentagon called Cloudy Office, which was based around the scenario of a terrorist attack at the Pentagon involving chemical weapons.

In February 2001, the FBI's Washington, DC, field office started sponsoring training with local fire department and law enforcement commanders on how emergency response workers and the FBI should coordinate their actions if there was a terrorist attack in the Washington area. Just two or three days before 9/11, the Washington field office and various other agencies held an exercise in Northern Virginia, based around the scenario of a terrorist attack involving chemical weapons.

And United Airlines, which had two of its planes hijacked on September 11, held a surprise exercise 12 days before 9/11 in which employees were led to believe one of their planes had crashed.

United Airlines personnel were subjected to a surprise training exercise 12 days before 9/11 in which they were led to believe that one of their planes had crashed. The exercise was so realistic that some of them ended up in tears or became physically sick. Consequently, on September 11, 2001, when two United Airlines planes were hijacked and then crashed, the manager who organized the exercise apparently thought his employees had mistaken reports about the terrorist attacks for part of an exercise and therefore told them, "This is not a drill!"

Furthermore, United Airlines had previously conducted other exercises that were based around scenarios resembling aspects of the 9/11 attacks, which may have caused its employees to be confused on September 11 over whether the crisis that day was real or simulated. The scenarios included hijackings and planes crashing into buildings.

From the History Commons Groups blog:

New entries have been added to the Complete 9/11 Timeline at History Commons, which cover various events relating to the 9/11 attacks. Many of them describe warnings about the danger posed by al-Qaeda that were given in the 12 months leading up to 9/11 and some describe events from the day of September 11, 2001, itself.

Donald Rumsfeld Was Concerned about a Possible 'Modern-Day Version' of Pearl Harbor

A couple of new timeline entries deal with Secretary of Defense Donald Rumsfeld's preoccupation, in the months before 9/11, with the Japanese attack on Pearl Harbor, Hawaii, in December 1941 that led America to enter World War II. In March 2001, Rumsfeld sent members of the Joint Chiefs of Staff a copy of the foreword to a book, which discussed the US government failures that led to the attack on Pearl Harbor. And in July that year, he wrote a note to himself in which he expressed his fear of the United States experiencing a "modern-day version" of the attack on Pearl Harbor.

Other senior officials talked, in the months before 9/11, about the possibility of a Pearl Harbor-like event happening in the future. In June 2001, Army General Tommy Franks, commander in chief of the US Central Command, gave a speech in which he said the US needed to prepare for an "asymmetric" attack resembling the attack on Pearl Harbor. And on the day before 9/11, Charles Nemfakos, deputy under secretary of the Navy, said during a briefing that the US would have to suffer an attack comparable to the attack on Pearl Harbor before it would address the problems with its defense policy.

Officials Warned about the Danger Posed by Al-Qaeda

NORAD's Northeast Air Defense Sector (NEADS) held a training exercise just over a month before September 11, 2001, which had some uncanny similarities to the 9/11 attacks. The exercise, called Fertile Rice, was based around the scenario of Osama bin Laden--the man who supposedly ordered the 9/11 attacks--organizing an aerial attack on a high-profile government building in Washington, DC--one of the cities attacked on September 11.

NEADS personnel were scheduled to take part in an exercise on September 11. We therefore need to consider whether the similarities between the scenario for the Fertile Rice exercise and some of the incidents they had to deal with on the morning of September 11 caused them to mistake real-world events for part of the day's exercise and thereby impaired their ability to respond to the 9/11 attacks.

EXERCISE INVOLVED BIN LADEN PLANNING TO ATTACK WASHINGTON WITH A DRONE AIRCRAFT

A number of senior officials in the United States government and military gave warnings in the week before September 11, 2001, or early on the morning of September 11, that seem to have predicted the 9/11 attacks with chilling accuracy.

These men--as is described below--voiced concerns that Osama bin Laden would carry out an attack in the U.S. in the near future; warned that an al-Qaeda attack that resulted in the deaths of hundreds of Americans could happen "at any time"; expressed concern that terrorists would attack the World Trade Center; warned about a "seminal event" occurring in the U.S. in which "hundreds, if not thousands" of Americans would be killed; said that "someone [is] going to attack us in a fashion we did not anticipate"; warned that "something big" was about to happen; and suggested the possibility of an attack taking place that would be equivalent to the Japanese attack on Pearl Harbor in 1941, in which over 2,400 Americans died.

Navy personnel at the Pentagon on the morning of September 11, 2001, including some key officials, appear to have acted with a surprising lack of urgency after they learned of the terrorist attacks on the World Trade Center.

Even though the Navy--along with the rest of the United States military--was responsible for protecting America if it was under attack, its personnel at the Pentagon seem to have done nothing, or very little, to help defend the country after they learned of the plane crashes at the World Trade Center. Remarkably, many of them continued with their normal work duties as if nothing unusual had happened. Furthermore, the Navy's top officials appear to have issued no orders to their personnel, regarding what to do in response to the crashes.

From the History Commons Groups blog:

A large number of entries have been added to the Complete 9/11 Timeline at History Commons, including many that provide new details about the events of September 11, 2001, and some that describe the initial official accounts of the military's response to the 9/11 attacks.

Air Force Secretary and Chief and Chief of Staff Learned of Attacks during Meetings

Several new timeline entries detail the actions of James Roche, the secretary of the Air Force, and John Jumper, the Air Force chief of staff, on September 11. Roche was alerted to the first plane crash at the World Trade Center during a meeting with several congressmen in his office at the Pentagon, in which the subject of Islamic fundamentalism was being discussed. Jumper, meanwhile, learned about the crashes at the WTC during a routine staff meeting, but he continued the meeting instead of responding right away.

After Jumper headed upstairs to Roche's office, the two men were escorted to the Air Force Operations Center in the basement of the Pentagon shortly after the building was attacked, at 9:37 a.m. When they arrived at the Operations Center, they started assisting the Air Force's response to the attacks.

A dozen Army personnel, including many senior officers, went ahead with a routine, previously scheduled meeting at 9:00 a.m. on September 11, 2001, in an area of the Pentagon that was severely damaged when the building was attacked at 9:37 a.m., even though a hijacked plane had crashed into the World Trade Center 14 minutes earlier and this incident had been reported on television since 8:49 a.m. Strangely, the officers were unaware of the crash when they went into their meeting and no one interrupted the meeting to let them know the U.S. was under attack after a second hijacked aircraft hit the World Trade Center at 9:03 a.m. They were consequently still continuing their meeting as if nothing was wrong, oblivious to the crisis that was taking place, when the Pentagon was hit and a huge fireball erupted into their room.

The immediate response to the 9/11 attacks of dozens of the most senior U.S. Air Force officials at the Pentagon who were together in a meeting when the attacks began appears to have been far from what we might reasonably expect, considering the serious and unprecedented crisis the officials had to deal with and the Air Force's key role in responding to it. Evidence suggests that after the first plane crash at the World Trade Center was reported on television on September 11, 2001, there was a delay of over 10 minutes before the officials' meeting was interrupted and the officials were alerted to the incident. The subsequent response of the officials appears to have been slow and lacking urgency.

More than 350 people who were originally scheduled to be on the four airliners hijacked in the 9/11 attacks either changed their plans and canceled their reservations--in many cases at the last minute--or simply failed to show up for the flights on the morning of September 11, 2001. While these individuals came from a variety of backgrounds, a remarkable number of them worked in, or had close connections to, Hollywood or other areas of the entertainment industry. Some of them were very well-known personalities.

For example, among the individuals who had reservations for American Airlines Flight 11--the first plane to be hijacked--were Seth Macfarlane, the creator of the cartoon Family Guy; actor Mark Wahlberg, the star of movies such as Boogie Nights and The Fighter; Bobby Farrelly, the writer and director of comedy movies such as Dumb & Dumber and There's Something About Mary; and Julia Child, the renowned chef and television personality. Sam Mendes, the director of American Beauty and the latest James Bond movie, Skyfall, was originally scheduled to be on American Airlines Flight 77, the third plane to be hijacked. And Robert Redford, the world-famous actor and director, narrowly avoided being on United Airlines Flight 93, the fourth plane to be hijacked.

Interestingly, one man who was originally booked on Flight 77--Erik Nelson--was later the executive producer of a National Geographic Channel documentary that attempted to debunk claims of U.S. government involvement in the 9/11 attacks.

It is also perhaps notable that a fair number of people who were originally scheduled to be on the hijacked flights but canceled their reservations or failed to turn up for their flights worked in professional sport. These included major league baseball player Brad Thomas, ice hockey coach Bruce Boudreau, and legendary basketball coach John Thompson.

Summarized in this article are accounts found in books, news articles, FBI documents, websites, or Internet blogs, of these individuals who were originally booked on the flights hijacked on September 11, but canceled their reservations or simply failed to show up for their flights.