The twin towers, as the north and south towers of World Trade Center in New York City were known, were destroyed in coordinated terrorist attacks on Sept. 11, 2001. Islamic extremists hijacked four commercial airliners that day, two of which were flown into the towers.
The first plane, American Airlines flight number 11 bound for Los Angeles from Boston, flew into the north tower, known as World Trade Center One, at 8:46 a.m. EST. A second plane, United Airlines flight number 175 also headed to Los Angeles from Boston, flew into the south tower, World Trade Center Two, 17 minutes later. The impacts of the aircraft and subsequent fires caused structural failure and collapse of the buildings.