Daniela Knafl was 9 years old when The September 11 attacks, a series of coordinated suicide attacks killing 2,996 people using four aircraft hijacked by 19 members of al-Qaeda. Two aircraft crash into the World Trade Center in New York City, a third crashes into The Pentagon in Arlington County, Virginia, and a fourth into a field near Shanksville, Pennsylvania. The September 11 attacks were a series of four coordinated terrorist attacks by the Islamic terrorist group al-Qaeda against the United States on the morning of Tuesday, September 11, 2001. The attacks killed 2,996 people, injured over 6,000 others, and caused at least $10 billion in infrastructure and property damage. Additional people died of 9/11-related cancer and respiratory diseases in the months and years following the attacks.