As noted above, the 9/11 plotters spent somewhere between $400,000 and $500,000 to plan and conduct their attack. The available evidence indicates that the 19 operatives were funded by al Qaeda, either through wire transfers or cash provided by KSM, which they carried into the United States or deposited in foreign accounts and accessed from this country. Our investigation has uncovered no credible evidence that any person in the United States gave the hijackers substantial financial assistance. Similarly, we have seen no evidence that any foreign government-or foreign government official-supplied any funding. We have found no evidence that the Hamburg cell members (Atta, Shehhi, Jarrah, and Binalshibh) received funds from al Qaeda before late 1999. It appears they supported themselves. KSM, Binalshibh, and another plot facilitator, Mustafa al Hawsawi, each received money, in some cases perhaps as much as $10,000, to perform their roles in the plot. After the Hamburg recruits joined the 9/11 conspiracy, al Qaeda began giving them money. Our knowledge of the funding during this period, before the operatives entered the United States, remains murky. According to KSM, the Hamburg cell members each received $5,000 to pay for their return to Germany from Afghanistan after they had been selected to join the plot, and they received additional funds for travel from Germany to the United States. Financial transactions of the plotters are discussed in more detail in chapter 7. Requirements for a Successful Attack As some of the core operatives prepared to leave for the United States, al Qaeda's leaders could have reflected on what they needed to be able to do in order to organize and conduct a complex international terrorist operation to inflict catastrophic harm. We believe such a list of requirements would have included leaders able to evaluate, approve, and supervise the planning and direction of the operation; communications sufficient to enable planning and direction of the operatives and those who would be helping them; a personnel system that could recruit candidates, vet them, indoctrinate them, and give them necessary training; an intelligence effort to gather required information and form assessments of enemy strengths and weaknesses; the ability to move people; and the ability to raise and move the necessary money. The information we have presented about the development of the planes operation shows how, by the spring and summer of 2000, al Qaeda was able to meet these requirements. By late May 2000, two operatives assigned to the planes operation were already in the United States. Three of the four Hamburg cell members would soon arrive. 
When did al Qaeda members plotting the 9/11 attacks arrive in the U.S.?
11