The September 11 attacks (often referred to as September 11th or 9/11) were a series of coordinated suicide attacks by al-Qaeda upon the United States on September 11, 2001. On that morning, 19 al-Qaeda terrorists hijacked four commercial passenger jet airliners. The hijackers intentionally crashed two of the airliners into the Twin Towers of the World Trade Center in New York City, killing everyone on board and many others working in the buildings. Both buildings collapsed within two hours, destroying nearby buildings and damaging others. The hijackers crashed a third airliner into the Pentagon in Arlington, Virginia, just outside Washington, D.C. The fourth plane crashed into a field near Shanksville in rural Pennsylvania, after some of its passengers and flight crew attempted to retake control of the plane, which the hijackers had redirected toward Washington, D.C. There were no survivors from any of the flights.
2,976 victims and the 19 hijackers died in the attacks. The overwhelming majority of casualties were civilians, including nationals of over 90 countries. In addition, the death of at least one person from lung disease was ruled by a medical examiner to be a result of exposure to dust from the World Trade Center's collapse.
The United States responded to the attacks by launching a War on Terrorism, invading Afghanistan to depose the Taliban, who had harbored al-Qaeda terrorists, and enacting the USA PATRIOT Act. Many other countries also strengthened their anti-terrorism legislation and expanded law enforcement powers. Some American stock exchanges stayed closed for the rest of the week following the attack, and posted enormous losses upon reopening, especially in the airline and insurance industries. The destruction of billions of dollars worth of office space caused serious damage to the economy of Lower Manhattan.
The damage to the Pentagon was cleared and repaired within a year, and the Pentagon Memorial was built on the site. The rebuilding process has started on the World Trade Center site. In 2006 a new office tower was completed on the site of 7 World Trade Center. 1 World Trade Center is currently under construction at the site and, at 1,776 ft (541 m) upon completion in 2013, it will become one of the tallest buildings in North America. Three more towers were originally expected to be built between 2007 and 2012 on the site. Ground was broken for the Flight 93 National Memorial on November 8, 2009, and the first phase of construction is expected to be ready for the 10th anniversary of the attacks on September 11, 2011.
The attacks had a significant economic impact on the United States and world markets. The New York Stock Exchange (NYSE), the American Stock Exchange (AMEX), and NASDAQ did not open on September 11 and remained closed until September 17. When the stock markets reopened, the Dow Jones Industrial Average (DJIA) stock market index fell 684 points, or 7.1%, to 8921, a record-setting one-day point decline.
By the end of the week, the DJIA had fallen 1,369.7 points (14.3%), its then-largest one-week point drop in history, though later surpassed in 2008 during the global financial crisis. U.S. stocks lost $1.4 trillion in value for the week. This is equivalent to $1.69 trillion in present day terms.
Economist and Crisis Consultant Randall Bell was retained by the city and state of New York to compute the economic damages to The World Trade Center site. He writes in his book, Strategy 360, "The World Trade Center damages, estimated by the New York City Mayor's Office, were staggering: Clean up and stabilization of the WTC site - $9.0 billion; Repairing and replacing damaged infrastructure - $9.0 billion; Rebuilding the World Trade Center as smaller buildings - $6.7 billion; Repairing and restoring other damaged buildings - $5.3 billion; Lost rent of the destroyed buildings - $1.75 billion."
In New York City, about 430,000 job-months and $2.8 billion in wages were lost in the three months following the 9/11 attacks. The economic effects were mainly focused on the city's export economy sectors. The city's GDP was estimated to have declined by $27.3 billion for the last three months of 2001 and all of 2002. The Federal government provided $11.2 billion in immediate assistance to the Government of New York City in September 2001, and $10.5 billion in early 2002 for economic development and infrastructure needs.
The 9/11 attacks also hurt small businesses in Lower Manhattan near the World Trade Center, destroying or displacing about 18,000 of them. Assistance was provided by Small Business Administration loans and federal government Community Development Block Grants and Economic Injury Disaster Loans. Some 31.9 million square feet of Lower Manhattan office space was damaged or destroyed.
Many wondered whether these jobs would return, and the damaged tax base recover. Studies of the economic effects of 9/11 show that the Manhattan office real-estate market and office employment were less affected than initially expected because of the financial services industry's need for face-to-face interaction.
North American air space was closed for several days after the attacks and air travel decreased upon its reopening, leading to nearly a 20% cutback in air travel capacity, and exacerbating financial problems in the struggling U.S. airline industry.
The thousands of tons of toxic debris resulting from the collapse of the Twin Towers consisted of more than 2,500 contaminants, including known carcinogens. This has led to debilitating illnesses among rescue and recovery workers, which many claim to be directly linked to debris exposure. For example, NYPD Officer Frank Macri died of lung cancer that spread throughout his body on September 3, 2007; his family contends the cancer is the result of long hours on the site and they have filed for line-of-duty death benefits, which the city has yet to rule on.
Health effects have also extended to some residents, students, and office workers of Lower Manhattan and nearby Chinatown. Several deaths have been linked to the toxic dust caused by the World Trade Center's collapse and the victims' names will be included in the World Trade Center memorial. There is also scientific speculation that exposure to various toxic products in the air may have negative effects on fetal development. Due to this potential hazard, a notable children's environmental health center is currently analyzing the children whose mothers were pregnant during the WTC collapse, and were living or working near the World Trade Center towers.