Although the various theories for the cause of 9/11 vary widely and include conspiracy theorists' contention that it was an inside job by the United States government, the majority of people believe it was meant to protest U.S. support of Israel as well as its Middle East military presence in general. Attackers were allegedly Islamic terrorists from several Middle Eastern nations financed by Osama bin Laden. Each of the 19 hijackers who together took control of four commercial airplanes intent on suicide attacks were associated directly with bin Laden's al-Qaida terrorism group.
Bin Laden declared a holy war against the United States in 1998. At that time, he called for the murder of American civilians in a fatwa he signed. Several Middle East scholars believe that 911 was bin Laden's way of provoking the U.S. into a war that would incite Muslims throughout the world to unite in opposition to the West.
Critics of the federal government contend that the failure to thwart 9/11 was the result of the U.S. government not sharing information among its various intelligence agencies, several of which had advanced warning of portions of the 9/11 plot.
Others blame lax airport security, pointing to the fact that the terrorists successfully smuggled knives and box-cutters onto planes at three airports on the East Coast.