Al-Shehhi spent his time making preparations for the attack itself , such as meeting with crucial planners abroad , assisting with the arrival of hijackers aboard the other flights , and travelling on surveillance flights determining details on how the hijacking would take place . On September 9 , 2001 , he traveled from Florida to Boston , where he stayed at the Milner Hotel until September 11 . After boarding United Airlines Flight 175 at Logan International Airport , al-Shehhi and 4 other hijackers waited 30 minutes into the flight to make their attack , which then allowed al-Shehhi to take over control as pilot , and at 9:03 a.m. , 17 minutes after Mohamed Atta crashed American Airlines Flight 11 into the North Tower , 23-year-old al-Shehhi crashed the Boeing 767 into the South Tower of the World Trade Center . He was the youngest hijacker-pilot to participate in the attacks . The impact of the Boeing 767 operating as United 175 into the South Tower was seen live on television as it happened . 56 minutes later at 9:59 a.m. , the 110-story skyscraper collapsed , killing hundreds of people , including around 900 office workers and first responders
American Airlines Flight 11
American Airlines Flight 11
Marwan al-Shehhi