The ensuing investigation was the largest in the history of the Bureau. The attacks led to far-reaching changes in the organization as it elevated terrorism to the gravest threat against the U.S.
The attacks took the lives of nearly 3,000 people, and the crash sites represented the largest crime scene in FBI history. At the peak of the case, more than half of all FBI agents were at work to identify the hijackers and their sponsors and, along with other agencies, to head off any possible future attacks.
Over the last 20 years, the Bureau evolved from an agency focused primarily on criminal offenses into an intelligence-based national security and law enforcement organization. Preventing terrorism continues to be the FBI’s top priority; the Bureau has established more than 200 Joint Terrorism Task Forces with partner law enforcement agencies across the country.
The events of 9/11 are forever etched in the minds of anyone old enough to remember the day. Those who were on the East Coast recall that it was a brilliant, clear morning. Then, at 8:46 a.m., American Airlines Flight 11 crashed into the North Tower of the World Trade Center in New York City.
In a meticulously planned attack, terrorists hijacked four airliners. They flew three of the planes into buildings: the twin towers of the World Trade Center in New York and the Pentagon in Arlington, Virginia. They crashed the fourth plane in rural Pennsylvania. The attacks killed 2,976 people and injured thousands more. Today, many first responders are still dealing with adverse health effects from working in toxic conditions.
This is the first in a series of stories about how 9/11 shaped today’s FBI.
The crash sites in New York, Virginia, and Pennsylvania represented the largest crime scene in FBI history. The ensuing investigation was also without precedent; at one point, more than half of all special agents were working on some aspect of the case.
Immediately after the attacks, the FBI’s top job was to identify the attackers and prevent another incident. Experts in terrorism, evidence collection, and other specialties worked feverishly to determine what had happened and who was responsible. The FBI also coordinated with its partners in law enforcement and the intelligence community domestically and abroad as it launched its most ambitious investigation ever.
Within minutes, officials at FBI Headquarters in Washington, D.C., activated the Strategic Information and Operations Center. By the end of the day, the FBI had established command posts for each of the three crash sites.
Thousands of agents interviewed witnesses and sources. They tracked down clues and tips worldwide to determine what had happened, who did it, and how future acts could be prevented. The FBI started identifying the 19 terrorists within hours.
Then-FBI Director Robert S. Mueller, III broke with routine and based the massive investigation out of FBI Headquarters instead of a field office. The PENTTBOM Team—short for Pennsylvania, Pentagon, and Twin Towers Bombing—coordinated the investigation out of a basement office, where dozens of agents would build a case against those responsible.
The case, which remains open, revealed extraordinary acts of courage and selflessness among the spectrum of responders. And it forever changed the way the FBI works with law enforcement and intelligence community partners to keep Americans safe in the U.S. and abroad.
“Because of that terrible day, starting in 2001 under the leadership of Director Mueller, the FBI transformed itself in ways that have made us stronger and better—and our country safer,” Director Christopher Wray said in 2019 during a visit to the National September 11 Memorial & Museum in New York City.
