. >> i'm charles gibson. >> i'm diane sawyer. it's september 11th, 2001. >> reporter: you hear somebody say, someone has just flown a plane into the world trade center. what was your immediate response? >> we did not appreciate or have the full knowledge that this was an airliner that was flown into the world trade center. >> we want to tell you what we know as we know it. we just got a report in that there's been some sort of explosion at the world trade center in new york city. >> we don't know if it would have been deliberate or accidental. we know so little now. >> it wasn't until we learned that the second aircraft -- >> my god. >> that looks like a second plane. >> that we ended our meeting. and then moved to where we could see those images on the television, like every other american. and that's when we knew our nation was under attack. >> reporter: what were your marching orders at that point? >> we needed to get armed missiles, built up and loaded on to our aircraft. and we also needed to get the authorization to launch.

around 8:52, i saw charles gibson and diane sawyer cutting away from local news to abc news at that time, and when i saw the second plane hit, i knew we were attacked and it reminded me of the challenger disaster, pearl harbor, dj, john f. kennedy's assassination, and it reminded me of munich in 1972 when the israeli athletes were killed. i was not born. i was born in 1976, the year we celebrated our bicentennial. host: isn't it amazing how you remember every detail of that day, and of the morning prior? caller: yes. i remember. in 1986, i was 10 years old. i remember the challenger exploded. i was in elementary school in the san fernando valley when the challenger disaster happened. we were told by teachers something like that. 15 years later, i was in hawthorne when the attacks happened. and when covid-19 happened, in the inland empire. i was born in 1976, when the bicentennial celebration happened. host: we are going to leave it there. you can see people arriving at the pentagon for one of the commemorations there. what does greta have for us? >> headlines from across the country, beg