The morning of 11 September 2001 nineteen terrorists took control of four passenger airliners traveling to California took off from Boston's Logan respectively, from Washington Dulles Dulles - but used for flights from Washington - and from Newark, New Jersey . The hijackers led two aircraft model Boeing 767, American Airlines Flight 11 and United Airlines Flight 175 crashed into the north and south towers of the World Trade Center. Another group of hijackers led American Airlines Flight 77 crashed into the Pentagon, while a fourth flight, the United Airlines Flight 93, with which the terrorists wanted to hit the Capitol or the White House in Washington, crashed near Shanksville, Pennsylvania .
During the hijacking, some passengers and crew members were able to make calls with the device radiotelephone air-surface of GTE and mobile phones; They claimed that several hijackers were aboard each plane, and that the terrorists had taken control of the aircraft using knives and box cutters to kill some flight attendants and at least one pilot or a passenger, including the captain of Flight 11.
A flight attendant for American Airlines 11, a passenger on Flight 175 and some passengers on Flight 93 reported that the hijackers had bombs, but one of the passengers also said to believe that it was inert ordnance. No traces of explosives were found on the sites of impact. The Report of the Commission on September 11 said the bombs were probably false.
United Airlines Flight 93 on the black box recordings revealed that crew and passengers attempted to wrest control of the plane to hijackers after learning, by telephone, that other hijacked planes had been sent to crash into some buildings.
According to the transcript of the recording, one of the hijackers gave the order to turn the aircraft when it was clear that he would lose control because of the passengers. Shortly after, the plane crashed in a field near Stonycreek, in the county of Somerset (Pennsylvania), at 10:03:11 local time (14:03:11 UTC). In an interview with Al Jazeera journalist Yosri Foda, Khalid Sheikh Mohammed, the al Qaeda leader, he said that the target of Flight 93 was the Capitol in Washington.
Three buildings of the World Trade Center collapsed due to structural damage. The south tower (2 WTC called) collapsed at 9:59 or so, after a 56-minute fire caused by the impact of United Airlines Flight 175; The north tower collapsed at 10:28, after a fire of 102 minutes. The fall of WTC 1 produced debris which damaged the nearby 7 World Trade Center, whose structural integrity was further compromised by the fire, which led to the collapse of the east penthouse at 17:20 local time on the same day; the entire building collapsed completely at 17:21 local time.
The National Institute of Standards and Technology promoted the investigations into the causes of the collapse of the three buildings, then widening the investigation of measures for the prevention of progressive collapse, wondering for example if the design had expected resistance to fire and if it had been made strengthening steel structures. The report about WTC 1 and WTC 2 was finished in October 2005, while the investigation of the WTC 7 was published on Aug. 21, 2008: the collapse of the building was caused by thermal expansion, produced by uncontrolled fires for hours of 'steel of the primary column, the number 79, the failure of which gave rise to a progressive collapse of the carrying structures nearby.
The attacks created great confusion among news organizations and air traffic controllers in the United States; to the entire international civil air traffic it was banned from landing on US soil for three days. The aircraft already in flight were rejected or routed to airports in Canada or Mexico. Radio and television stations spread unconfirmed and often contradictory throughout the day; one of the most widespread reconstructions told of a car bomb exploded in the Secretariat of State of the United States in Washington.
Shortly after announcing for the first time the Pentagon crash, CNN and other broadcasters also told that a fire had broken out at the National Mall in Washington.  Another report was released by the Associated Press, according to which a Boeing 767 Delta Air Lines, Flight 1989 was hijacked: this news item turned out to a mistake, as it was actually thought that there was the danger, but the plane responded to the commands of the flight controllers and landed in Cleveland, Ohio.
The victims of the attacks were 2,974, excluding nineteen hijackers: 246 on the four planes (87 on American Airlines Flight 11, United Airlines Flight 175 on 60, 59 on American Airlines Flight 40 and United Airlines Flight 93; there was no survivor) , 2603 in New York and 125 at the Pentagon.
All the victims were civilians, except for 55 military personnel killed at the Pentagon. Were more than 90 countries that lost citizens in the attacks on the World Trade Center.
At least 200 people jumped from the burning towers and died, as depicted in the iconic photo The Falling Man ("Falling Man"), falling on streets and rooftops of nearby buildings, hundreds of meters below. Some people who were in the towers above the impact points went up to the roofs of the buildings, hoping to be rescued by helicopter, but the access doors to the roof were locked; Moreover, there was no bailout with helicopters and, that morning of September 11, the thick smoke and the high heat of the fire would have prevented helicopters to perform rescue operations.
It was possible to identify the remains of only 1,600 of the victims of the World Trade Center; medical offices also collected "about 10,000 fragments of unidentified bone and tissue, which can not be linked to the list of deaths." Other remains of bones were found again in 2006, while the workers approntavano the Deutsche Bank Building for demolition.
Death from lung disease to some other people has been traced back to breathing dust containing hundreds of toxic compounds (such as asbestos, mercury, lead, etc.) Caused by the collapse of the World Trade Center. The severity of the environmental pollution caused by such dust - that invested the entire southern tip of Manhattan - was made known to the public only at a distance of about four years after the event: until then, the US government agencies had underestimated or hidden environmental risks, perhaps in order not to cause further panic and make it sent relief, clearing rubble, restore normal activities of the city so badly injured