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.
American Airlines Flight 77
On the morning of September 11, 2001, the five hijackers arrived at Washington Dulles International Airport. At 07:15, Khalid al-Mihdhar and Majed Moqed checked in at the American Airlines ticket counter for Flight 77, arriving at the passenger security checkpoint a few minutes later at 07:18. Both men set off the metal detector and were put through secondary screening. Moqed continued to set off the alarm, so he was searched with a hand wand. The Hazmi brothers checked in together at the ticket counter at 07:29.[Hani Hanjour checked in separately and arrived at the passenger security checkpoint at 07:35. Hanjour was followed minutes later at the checkpoint by Salem and Nawaf al-Hazmi, who also set off the metal detector's alarm. The screener at the checkpoint never resolved what set off the alarm. As seen in security footage later released, Nawaf Hazmi appeared to have an unidentified item in his back pocket. Utility knives up to four inches were permitted at the time by the Federal Aviation Administration (FAA) as carry-on items. The passenger security checkpoint at Dulles International Airport was operated by Argenbright Security, under contract with United Airlines.