11 September 2001
On 11 September 2001 thousands were killed after terrorists crashed hijacked airliners into the World Trade Centre in New York and the Pentagon in Washington. Four planes were hijacked in total, two were flown into the World Trade Centre, one into the Pentagon and the fourth crashed into a field in Pennsylvania. Trading on Wall Street stopped and the Federal Aviation Administration halted all flight operations at the nation's airports for the first time in U.S. history. In the immediate aftermath of the attacks, the Bush administration declared a 'war on terrorism', with the stated goals of bringing Osama bin Laden and al-Qaeda to justice and preventing the emergence of other terrorist networks. The affects were felt world wide. Numerous countries, including the United Kingdom, India, Australia, France, Germany, Indonesia, China, Canada, Russia, Pakistan, Jordan, Mauritius, Uganda and Zimbabwe introduced "anti-terrorism" legislation and froze the bank accounts of businesses and individuals they suspected of having al-Qaeda ties. In South Africa, flights to the USA were suspended, security measures at airports tightened, and the economy was adversely affected.  
References

Archives of Global Change in the 21st Century, September 11, 2001-The Day the World Changed [online], Available at www.september11news.com [Accessed: 10 September 2013]