Born in Saudi Arabia, Hamza al-Ghamdi left his family to fight in Chechnya and was probably sent to Al-Qaeda training camps in Afghanistan where he was chosen to participate in the 9/11 attacks.

He arrived in the United States in May 2001 on a tourist visa. On 11 September 2001, al-Ghamdi boarded United Airlines Flight 175 and hijacked the plane along with his older brother Ahmed al-Ghamdi and 3 other terrorists so that lead hijacker and trained pilot Marwan al-Shehhi could crash into WTC 2.