In case you don't recall the events of Sept. 11, 2001.

8:46 a.m.

The first airplane crashed into the north tower of the World Trade Center in New York City.

9:03 a.m.

The second airplane crashed into the south tower of the World Trade Center.

9:43 a.m.

The third airplane crashed into the Pentagon in Washington, D.C.

10:05 a.m.

The south tower of the World Trade Center collapsed.

10:10 a.m.

The fourth airplane crashed into a field in Somerset County, Pennsylvania

10:28 a.m.

The north tower collapsed.

5:20 p.m.

A third building at the World Trade Center collapsed.