George W Bush: Threats are also growing within our borders

It is no coincidence that Bush, who was president at the time of the deed, spoke from Shanksville.

On September 11, 2001, the plane that came to be known as "Flight 93" crashed on an empty field outside the city, after passengers and crew overpowered the plane's hijackers.

In his speech, Bush said that the passengers and crew of Flight 93 must be remembered, even though many are still struggling with grief.

- We learned that Americans are vulnerable, but not fragile.

We learned that they possess a strength that survives the worst life can give.

We learned that courage is more common than we could have previously imagined, he said.

Bush also stressed that the threats to the United States as a country still remain, but also that extremism is not only growing outside the country's borders.

- The security measures that have become part of our lives give us security, but also remind us of our vulnerability.

"We have seen growing evidence that the dangers that threaten our country not only cross our borders, but also grow within the country," Bush said.