On September 11, 2001, a military helicopter flies over the Pentagon after an airplane crashed into the building following similar attacks on the World Trade Center in New York.
On September 11, 2001, a military helicopter flies over the Pentagon after an airplane crashed into the building following similar attacks on the World Trade Center in New York. Chuck Kennedy / MCT
On September 11, 2001, a military helicopter flies over the Pentagon after an airplane crashed into the building following similar attacks on the World Trade Center in New York. Chuck Kennedy / MCT

Experts: Terrorism threat to U.S. now more homegrown

September 10, 2010 6:27 PM