I'd also recommend taking a look at "The Only Plane in the Sky" by Garrett Graff, which is an oral history of 9/11; basically, a huge number of in-person interviews that construct a timeline of the days leading up to, during, and after 9/11, including those of the pilots who went up in the fighters, knowing that should they need to, mid-air collision was the only option if they needed to intercept something. For what it's worth: a great read, but a tough one. I'm sure you won't have trouble finding a book link, but Politico [1] has an excerpt if you're interested.

[1] https://www.politico.com/magazine/story/2016/09/were-the-onl...