The September 11 attacks, also commonly referred to as 9/11, were a series of four coordinated terrorist attacks by the militant Islamist terrorist group al-Qaeda against the United States on the morning of Tuesday, September 11, 2001. On that morning, four commercial airliners traveling from the northeastern U.S. to California were hijacked mid-flight by 19 al-Qaeda terrorists. The hijackers were organized into three groups of five hijackers and one group of four. Each group had one hijacker who had received flight training and took over control of the aircraft. Their explicit goal was to crash each plane into a prominent American building, causing mass casualties and partial or complete destruction of the targeted buildings.
The first plane to hit its target was American Airlines Flight 11. It was flown into the North Tower of the World Trade Center complex in Lower Manhattan at 8:46 am. Seventeen minutes later at 9:03 am, the World Trade Center's South Tower was hit by United Airlines Flight 175.