9/11 at 25: How the September 11 Attacks Changed US Security Forever

Twenty-five years ago, four hijacked passenger planes turned an ordinary September morning in the United States into one of the deadliest days in the country’s history, killing 2,977 people and triggering a sweeping overhaul of national security.

At 8:46am on September 11, 2001, American Airlines Flight 11 crashed into the North Tower of the World Trade Center in New York. Seventeen minutes later, United Airlines Flight 175 struck the South Tower. At 9:37am, American Airlines Flight 77 hit the Pentagon, while United Airlines Flight 93 later crashed into a field near Shanksville, Pennsylvania, after passengers and crew tried to regain control of the aircraft.

The attacks exposed major weaknesses in US aviation security, intelligence-sharing, emergency communications and coordination. By the end of the day, 2,977 people had been killed, including 2,753 at the World Trade Center, 184 at the Pentagon and 40 near Shanksville. The victims included 343 firefighters and paramedics, 23 New York Police Department officers and 37 Port Authority police officers.

The plot had been years in the making. A US House Homeland Security Committee review said planning dated back to at least 1999, when Osama bin Laden and his associates discussed using commercial aircraft as weapons. Hijackers later obtained US visas, attended flight schools and conducted surveillance of potential aircraft and targets. Several passed through airport security on the morning of the attacks, despite some being selected for additional screening.

The attacks prompted rapid changes in the way America approached homeland security. Eleven days later, President George W. Bush appointed Pennsylvania Governor Tom Ridge as the first director of the White House Office of Homeland Security. Congress subsequently created the Transportation Security Administration (TSA), placing aviation security under federal oversight instead of the previous system in which airlines relied on private contractors for passenger and baggage screening.

A broader restructuring followed with the creation of the Department of Homeland Security (DHS) in 2002. The department brought together all or parts of 22 existing agencies and took responsibility for areas including counterterrorism, intelligence, border security, transportation security, cybersecurity and emergency preparedness.

Law enforcement also expanded its counterterrorism capabilities. The FBI’s Joint Terrorism Task Forces became a major channel for intelligence-sharing between federal, state and local agencies, while police departments across the country developed dedicated counterterrorism units and expanded their intelligence operations.

The US also established the 9/11 Commission to investigate how the attacks occurred and recommend measures to prevent future attacks. Its 2004 report produced 41 recommendations, several of which were later implemented through legislation and executive action.

Now, 25 years after the attacks, US security officials say the threat has evolved. The House Homeland Security Committee has identified lone actors, cyberattacks, artificial intelligence, transnational crime, border vulnerabilities and changing terrorist tactics among emerging challenges. Its latest review includes more than 20 recommendations covering intelligence-sharing, cybersecurity, AI risks, border security, emergency preparedness and other areas.

Committee Chairman Andrew R. Garbarino said the progress made since 9/11 must be matched by continued vigilance. The central lesson of September 11, he said, remains the need for the United States to adapt as threats change.