Here is a question about this article: The city and surrounding area suffered the bulk of the economic damage and largest loss of human life in the aftermath of the September 11, 2001 attacks when 10 of the 19 terrorists associated with Al-Qaeda piloted American Airlines Flight 11 into the North Tower of the World Trade Center and United Airlines Flight 175 into the South Tower of the World Trade Center, and later destroyed them, killing 2,192 civilians, 343 firefighters, and 71 law enforcement officers who were in the towers and in the surrounding area. The rebuilding of the area, has created a new One World Trade Center, and a 9/11 memorial and museum along with other new buildings and infrastructure. The World Trade Center PATH station, which opened on July 19, 1909 as the Hudson Terminal, was also destroyed in the attack. A temporary station was built and opened on November 23, 2003. A permanent station, the World Trade Center Transportation Hub, is currently under construction. The new One World Trade Center is the tallest skyscraper in the Western Hemisphere and the fourth-tallest building in the world by pinnacle height, with its spire reaching a symbolic 1,776 feet (541.3 m) in reference to the year of American independence.
What is the answer to this question: How many leader terrorists of Al Quada were involved with the 9/11 attacks directly that day?
10