Could 9/11 happen again? It depends on the meaning of the question. Could another coordinated air attack by hijack passenger jumbo jets strike the Pentagon and the World Trade Center or any other major structure? No, I don’t think so. Could another devastating coordinated terrorist attack against a major infrastructure system occur on American soil? Absolutely.
Since 9/11 airport and air travel security has increased tremendously. The federal government has taken steps to improve security at U.S. airports and say it is constantly testing the effectiveness of those measures. Among the steps that have been taken at airports across the country are the following:
The federal government has taken over security checkpoints and screeners are better trained. Checked luggage is now examined for explosives by machine, by hand, or by trained bomb-sniffing dogs. Every large passenger plane in the United States now has a cockpit door designed to withstand bullets and small explosives. Thousands of air marshals have been trained and deployed. Pilots can apply to become a federal flight deck officer, allowing them to carry a loaded gun and act as a federal officer aboard the plane. Workers who have access to the tarmac now must undergo background checks. Airplanes underwent major overhauls: Fortified cockpit doors were introduced, and first-class cabin curtains were dropped by some airlines. There are no-fly lists and a supra apparatus, the Department of Homeland Security dedicated to maintaining readiness, prevention, and detection systems.
Despite all the country's sometimes controversial enhanced security precautions, a substantial majority of Americans (61%) in a 2011 Rasmussen poll believed a similar-scale attack is at least somewhat likely to occur on the homeland during the next 10 years. This includes nearly a third of Americans (29%) who think such a deadly repeat assault is very likely.
Today, according to a Rasmussen poll, 64% of American adults think a bigger threat now to the United States is a domestic attack. Just 18% believe an attack from terrorists outside the United States is a bigger threat.
Risk managers and disaster recovery specialists echo the concerns represented by the polls. A report published by knowledge@Wharton Law and Public Policy, says that although new government policies along with efforts at disaster planning by private companies aimed at preventing another horrific day like 9/11 have increased, questions remain over how best to protect valuable assets -- from buildings to computer systems to people. Indeed, the "report card" released by the former 9/11 Commission chairmen identified nine major recommendations from their initial report that have yet to be sufficiently implemented, including a unified framework for training emergency personnel and responding to crises. "In 2005, Hurricane Katrina revealed that a catastrophic natural disaster could produce a chaotic and disorganized response by all levels of government, causing large-scale human suffering. A decade after 9/11, the nation is not yet prepared for a truly catastrophic disaster," the report concluded.
A recent study by statisticians Aaron Clauset and Ryan Clauset suggests there's a 50% chance that another 9/11-scale attack will happen again, within the next 10 years. George Dvorsky of io9.com wrote to help them make their assessment; they gathered a global database of 13,274 terrorist events dating from 1968 to 2007. Then, rather than treating 9/11 as an outlier event, they created a statistical algorithm for estimating the probability of similarly large events (including global terrorism) within complex social systems. Their broad-scale and long-term probabilistic approach is similar to the one used in seismology, forestry, hydrology, and natural disaster insurance.
Jerome Bjelopera a specialist in organized crime and terrorism, in a CRS Report for Congress, entitled, The Domestic Terrorist Threat: Background and Issues for Congress found that domestic terrorism is a growing threat in America and it does not receive enough attention. Bjelopera notes that domestic terrorists have been responsible for orchestrating more than two-dozen incidents since 9/11, and there appears to be a growth in anti-government extremist activity as measured by watchdog groups in the last several years. He says that a large number of domestic terrorists do not necessarily use tactics such as suicide bombings or airplane hijackings.
American infrastructure and/or systems are highly exposed to a terrorist attack. Cyber terrorism is a growing concern amongst law enforcement officials. According to the FBI, cyber terrorism is any "premeditated, politically motivated attack against information, computer systems, computer programs and data which results in violence against non-combatant targets by sub-national groups or clandestine agents." Possible cyber terrorist targets include the banking industry, military installations, power plants, air traffic control centers, and water systems.
Critical public infrastructure (i.e., power plants, water purification plants, water treatment facilities, local government buildings) is an obvious target for terrorists. The Northeast blackout of 2003, which at the time was the second most widespread blackout in history, highlighted a vulnerable infrastructure single point of weakness. An eco-terrorist attack on the Gulf of Mexico would have a devastating effect on American trade. An attack on New York City’s mass transit system could throw the city and much of the world’s financial center into chaos.
The FBI has a public awareness program to educate on how to help prevent terrorist attacks. FEMA’s Cyber Terrorism Defense Initiative educates and trains public safety professionals on important concepts in securing public safety networks.
Security and law enforcement experts believe that it is unlikely that another 9/11 attack is possible. They are not as certain about other forms of attack.