sight of the pentagon hit by a jetliner 20 years ago signaled the beginning of a day of tributes. reporter: it s one of three sites where americans gathered in sommer remembrance, honeering each one of the 2977 people killed in the terrorist attacks on september 11th. at the footprints where the twin towers stood over manhattan president biden and the first lady were joined by the obamas in a sea of 9/11 families to memorialize those lost two decades ago. at 8:46 a.m. the first of six moments of silence marking the instant the first hijacked airliner struck the north tower. sara was a flight attendant on that plane. we redrcite the names of tho we lost, that memory goes back to that terrible day when it felt like an evil spector had descended on our world.
spoke directly to the uncle she never met and imagined how he might be today. hi, uncle, and know you re every day watching over us. and even though i never met you in person i still miss you a lot. i m sure if you were here yii d probably be doing them with you. there s a look at new york city right now. two brilliant shafts of light where the twin towers once stood in lower manhattan. the president and first lady paying their respects to the victims at all three sites, new york, virginia and pennsylvania. we begin our coverage with cnn s paulo sandoval in new york. reporter: at dawn the unfurling of a flag over the pentagon hit by a jetliner 20 years ago signaled the day of