people affected by this, it brings back the moment you got the phone call, the brings back the instant you got the news no matter how many years go by. reporter: he followed former president bush acknowledging the heroes of 9/11 in his keynote address at flight 93 memorial. >> these americans were brave, strong and you united in ways that shocked the terrorists. this is the nation we know. reporter: also in shanksville, vice president kamala harris remembered the resilience of the 40 passengers of flight 93. >> the most dire of circumstances, the 40 spend -- responded as one. they fought for their own lives, to save the lives of countless others. reporter: president biden ended the day by laying a wreath at the pentagon crash site. as the 9/11 tribute in light shined through the new york city