This year marks 25 years since the September 11 terrorist attacks, which killed 2,977 people. That series of coordinated attacks remains a defining part of American memory. In a recent YouGov survey, 64 percent of Americans said 9/11 changed the United States completely. The 9/11 Memorial & Museum estimates that 100 million Americans are too young to remember the day. That shift from lived experience to history may matter: 54 percent of Americans told YouGov that people born after 2001 generally do not have a good understanding of the attacks.
Conspiracy theories began spreading almost immediately after the attacks, which is not unusual after a major tragedy. Fear and uncertainty can create an opening for claims that promise simple answers to complicated questions.
What Are the Most Common 9/11 Conspiracy Theories?
Among the best-known 9/11 conspiracy theories are claims that explosives, rather than the planes and resulting fires, brought down the Twin Towers. Another says that a missile struck the Pentagon instead of American Airlines Flight 77. A third alleges that the U.S. military shot down United Airlines Flight 93. The remaining theories claim that the government deliberately allowed the attacks to happen, or that traders with advance knowledge profited from unusual activity in airline stocks.
These claims often begin with questions such as why the buildings collapsed, why the military failed to intercept the planes, or why suspicious stock trades occurred. They then make a leap from unanswered questions or unusual details to an elaborate hidden plot.
How 9/11 Conspiracy Theories Fueled Hate and Collective Blame
The search for someone to blame did not remain online. In the aftermath of the attacks, Muslims and Arab Americans faced harassment, threats, surveillance, and violence. Sikh and other South Asian Americans were also targeted, often because attackers wrongly assumed they were Muslim. Anti-Muslim hate crimes rose sharply, and the Justice Department later investigated more than 800 incidents involving violence, threats, vandalism, and arson against Muslims, Sikhs, Arab Americans, South Asian Americans, and others perceived to belong to these groups. Twenty-five years later, the effects of that backlash are still widely recognized: 52 percent of Americans say Muslims in the U.S. have been treated worse than people of other religions since 9/11, according to the same YouGov survey.
How Antisemitic 9/11 Conspiracy Theories Target Jews
The attacks also fueled a different form of collective blame against Jews. While Muslims, Arabs, Sikhs, and South Asians were often targeted as though they shared responsibility for the actions of al-Qaeda, antisemitic conspiracy theories cast Jews and Israel as the hidden architects of the attacks themselves. These claims alleged that Jews had planned, enabled, or profited from 9/11, turning the same tragedy into a vehicle for a very different form of hate.
From August 2020 through the present, the Blue Square Alliance Against Hate Command Center has tracked four million online conversations involving antisemitic 9/11 conspiracy theories. These claims appeared in online discussions every year during that period, but following the October 7 attacks, the Command Center found that their average conversation volume increased by 1,218 percent.
The Larry Silverstein and 9/11 Insurance Conspiracy Theory
One theory, which has been mentioned online more than 60,000 times over the past six years, centers on Jewish businessman Larry Silverstein, whose company had recently leased the World Trade Center. Conspiracists claim that Silverstein helped arrange the destruction of the towers to collect insurance money and worked with Mossad to carry it out. There is no credible evidence to support this claim.
The False Claim That 4,000 Jews Were Warned About 9/11
Another false rumor claims that 4,000 Jewish employees were warned to stay home on September 11. Jewish people were among those killed in the attacks, and fact-checkers have found no evidence of any mass warning. The rumor turned the deaths of thousands of people, including Jewish victims, into supposed proof of Jewish involvement.
The Mossad 9/11 Conspiracy Theory
Another theory, which accounts for roughly 50 percent of the antisemitic 9/11 conspiracy conversation we tracked, alleges that Mossad knew about or helped plan the attacks. There is no credible evidence that Israel or Mossad participated in planning or carrying out the attacks. A short account published by The Los Angeles Times noted Israeli intelligence had passed along general warnings about a possible al-Qaeda attack, but those warnings did not identify the specific plan in time to stop it.
Why Challenging 9/11 Misinformation Still Matters
As fewer Americans remember September 11 firsthand, the responsibility to preserve an accurate account of what happened becomes more important, not less. That means not only remembering the victims and the events of that day but also challenging the conspiracy theories and collective blame that followed and continued to find new audiences online.
