GALLERY: AC Remembers 9/11 on 22nd Anniversary
On the morning of Sept. 11, 2001, the twin towers of the World Trade Center in lower Manhattan crumbled after being hit by Boeing 767s flown by hijackers.

On the morning of Sept. 11, 2001, the twin towers of the World Trade Center in lower Manhattan crumbled after being hit by Boeing 767s flown by hijackers.