United Flight 93 was the plane that crashed in a field in Pennsylvania on 9/11. It was headed for some important federal building in Washington DC, but was detoured to the ground directly below it because of the intrepid actions of the plane's passengers and flight crew. They sacrificed their lives to prevent a (potentially) greater tragedy.

I think the connection op is making is that collective action and bravery can, even in the 11th hour, prevent a larger disaster.