Mohammed Mana Ahmed al-Qahtani ( ) ( sometimes transliterated as al-Kahtani ) ( born November 19 , 1979 ) is a Saudi citizen who has been detained as an al-Qaeda agent for ( since June 2002 ) in the United States 's Guantanamo Bay detention camps in Cuba . Qahtani allegedly tried to enter the United States to take part in the September 11 attacks as the 20th hijacker and was due to be onboard Flight 93 along with the four other hijackers . He was refused entry due to suspicions that he was trying to illegally immigrate . He was later captured in Afghanistan in the battle of Tora Bora in December 2001
September 11 attacks
September 11 attacks
Mohammed al-Qahtani