In the spring of 1999, osama bin laden (1957–), the head of the al-Qaeda terrorist group, agreed to support a plan submitted by Khalid Sheikh Mohammed (1964–) to use airplanes as weapons to crash into buildings, or what they came to call the “planes operation.” In the months that followed, they selected targets, including the World Trade Center in New York City and the White House, the Capitol, and the Pentagon in Washington. As the plans matured, bin Laden picked a group of young men who had attended al-Qaeda training camps in Afghanistan – Mohamed Atta, Nawaf al-Hazmi, Ziad Jarrah, Khalid al-Mihdhar, and Marwan al-Shehhi – to pilot the aircraft. The planning was done in extreme secrecy. None of these individuals knew how to pilot an aircraft, however, so two essential steps for the operation to succeed were to get them into the United States and to get them trained as pilots. Could U.S. intelligence analysts detect what was going on in time to prevent an attack in the United States?

Two of the intended pilots, Hazmi and Mihdhar, had fought with their fellow Muslims in Bosnia earlier in the decade, in addition to having traveled to Afghanistan for training. Therefore, intelligence analysts were likely to see them as suspicious. Nonetheless, they were granted visas by the State Department.