Suicide attack
The September 11, 2001 attacks, orchestrated by al-Qaeda, has been called "the worst attack on American soil since the Japanese attack on Pearl Harbor which thrust the United States into World War II". They involved the hijacking of four large passenger jet airliners because their long transcontinental flight plans meant they carried more fuel, allowing a bigger explosion on impact (unlike earlier airline hijackings, the primary focus was the planes, not the passengers). Two planes were deliberately flown into the Twin Towers of the World Trade Center in New York City, destroying both 110 story skyscrapers within less than two hours, and a third was flown into the Pentagon in Arlington County, Virginia, causing severe damage to the west side of the building. These attacks resulted in the deaths of 221 people (including the 15 hijackers) on board the three planes as well as 2,731 more in and around the targeted buildings. A fourth plane crashed into a field near Shanksville, Pennsylvania, after a revolt by the plane's passengers, killing all 44 people (including the four hijackers) on board. In total, the attacks killed 2,996 people and injured more than 6,000 others. The U.S. stock market closed for four trading days after the attacks (the first time it had an unscheduled closing since the Great Depression). Nine days after the attack, U.S. President George W. Bush called for a "War on Terror" and shortly thereafter launched the War in Afghanistan to find and capture Osama bin Laden, the head of the al-Qaeda organization that mounted the 9/11 attacks.
After the U.S.-led invasion of Iraq in 2003, Iraqi and foreign insurgents carried out waves of suicide bombings. More attacks have been carried out in Iraq (1938 as of mid-2015) than in any other country.
Eleanor J. Hill
According to U.S. State Department cable of February 2010, released by WikiLeaks in 2011, the FBI has investigated another suspect, Mohammed al-Mansoori, who had associated with three Qatari citizens who had flown from Washington to London on the eve of the attacks, after allegedly surveying the World Trade Center and the White House. U.S. law enforcement officials said that the information about the four men was "just one of many leads that were thoroughly investigated at the time and never led to terrorism charges". An official added, however, that the three Qatari citizens have never been questioned by the FBI. Eleanor Hill, the former staff director for the congressional joint inquiry on the September 11 attacks, said the cable reinforces questions about the thoroughness of the FBI's investigation. She also said that the inquiry concluded that the hijackers had a support network that helped them in different ways. The three Qatari men were booked to fly from Los Angeles to Washington on Sept. 10, 2001, on the same plane that was hijacked and piloted into the Pentagon on the following day, but did instead fly from Los Angeles to Qatar, via London. While the cable states that Mansoori would be currently under investigation, U.S. law enforcement officials said that was no active investigation of him or of the Qatari citizens mentioned in the cable.