The worst terrorist attack of all time is the September 11 attacks. This attack took place on Tuesday, September 11, 2001 around 8:46 a.m. – 10:28 a.m. ( EDT ). It was a series of four terrorist attacks by the Islamic terrorist group al-Qaeda against the United States.
19 al-Qaeda terrorists hijacked two aeroplanes, one from American Airlines Flight 11 and another from United Airlines. Both were crashed into the North and South towers of the World Trade Center. The towers collapsed in less than 2 hours of the attacks.
The attacks killed about 2,996 people, injured over 6,000 people , and caused a lot of infrastructure and property damage. It was also recorded that many people died of 9/11-related cancer and respiratory diseases in the months and years following the attacks.