The terrorist group al-Qaeda coordinated suicide attacks on the US. They hijacked four airplanes, crashing two into the World Trade Center Towers, another into the Pentagon and a fourth (probably destined for the White House or the Capitol) near Shanksville, Pennsylvania. Some people trapped in the World Trade Center walked up stairways to the roof hoping for helicopter rescue, but the door was locked. Emergency responders’ radios were incompatible. Hundreds of responders were killed or injured. The popularity of President George W. Bush and New York Mayor Rudy Giuliani soared. The Patriot Act was passed. Sikhs wearing turbans were assaulted and one killed. There was a firebombing at a Hindu temple. The invasion of Afghanistan and Iraq followed.
2976 victims, 19 hijackers dead, 6,000 injured, incalculable counter-terrorism costs. The US war on terror and stronger anti-terrorist laws in many countries. Incalculable financial cost, but direct rebuilding-cost was perhaps in excess of $30 billion with another $30 billion in lost GDP in New York alone. 18,000 small businesses were destroyed or displaced. 31.9 million square feet of Lower Manhattan office space was damaged or destroyed. Negotiation and fighting over rebuilding the site and a memorial to victims lasted more than a decade.
The apparent and confessed mastermind of the 2001 attack was involved in the 1993 World Trade Center bombing and related to the lead bomber in that attack. The event could have been predicted, since the same building had been bombed before and there had been numerous airplane hijackings and bombings in the US and of US installations around the world. White House perimeter security is breached regularly, even as late as under the Obama administration. The day of the event, Cold War responses were still in place with military scanning and reactions tens of thousands of feet up in the air and out over the Atlantic, but not 500 feet up and north over the Hudson River. When you build the world’s tallest building, you build risk into the system.