A group of terrorists hijacked four airplanes, sending two of them into the World Trade Center towers and another into the Pentagon -- with the other flight crash landing in a Shanksville, Pennsylvania, field.
9/11 ANNIVERSARY: 18 years later, America vows to 'never forget'
There were 2,977 innocent lives lost.
It is a day that will never be forgotten in the hearts of the American people.
Here's a look back at the September 11 attacks by the numbers.
- 2,977 people were killed
- 2,753 died at the World Trade Center Site
- 343 of them were New York City firefighters
- 23 were NYPD officers
- 37 were police officers from the Port Authority of New York and New Jersey
- 184 people were killed when American Airlines Flight 77 crashed into the Pentagon
- 40 were killed on United Airlines Flight 93 that crashed near Shanksville, Pennsylvania
- Countless victims and first responders are still dying due to 9/11-related illnesses
- 19 men hijacked 4 planes
- 60 percent of the World Trade Center victims' remains have been identified as of Sept. 2019
PHOTOS: 9/11 attacks on the World Trade Center in New York City