Al-Qaeda executed the September 11 attacks.
September 11 attacks . were a series of four coordinated terrorist attacks by the Islamic terrorist group al-Qaeda on the United States on the morning of Tuesday , September 11 , 2001 . The destruction of the World Trade Center and nearby infrastructure caused serious damage to the economy of Lower Manhattan and had a significant effect on global markets , closing Wall Street until September 17 and the civilian airspace in the U.S. and Canada until September 13 . World Trade Center (1973–2001) . On the morning of September 11 , 2001 , Al-Qaeda-affiliated hijackers flew two Boeing 767 jets into the North and South Towers within minutes of each other ; two hours later , both had collapsed .