People nationwide will pause Sunday to mark the 15-year anniversary of the September 11 terrorist attacks on our country. On that day in 2001, 19 militants associated with the Islamic extremist group al-Qaeda, hijacked four airliners and carried out suicide attacks against targets in the United States. The terrorists crashed two of those planes into the World Trade Center Towers in New York City, a third plane hit the Pentagon and a fourth plane crashed in a field in Pennsylvania. The crashed killed more than 3,000 people. Here's a look at The Tribute in Light placed next to the World Trade Center to mark the somber anniversary. The display creates two vertical columns of light in remembrance of those who died on 9/11.