The terrorists chose September 11 for the 2001 attacks primarily for strategic and practical reasons rather than symbolic ones. Key factors included the desire to strike quickly once the hijackers were prepared, to avoid detection; the timing ensured that the U.S. Congress would be in session (early September after Labor Day) so targets like the Capitol would be occupied; and the choice of a weekday maximized casualties in the Twin Towers, which were significant American symbols. The specific decision on September 11 appears to have involved some elements of chance, such as flight availability or other logistics, with no clear symbolic significance publicly confirmed by the attackers themselves. The planning was led by Khalid Sheikh Mohammed and Osama bin Laden, who focused on maximizing damage against key U.S. targets symbolic of American power.
The attacks were motivated by al-Qaeda's grievances against U.S. foreign policy, military presence in the Middle East, and support for Israel, among other reasons, intending to cause massive impact and attention.
