It might be worth doing some reading on the actual events of that day. For example, "being shot down by a fighter jet" wasn't an option; the fighters weren't armed when they were put up in the sky. The pilots in them went up knowing that if a plane needed to be taken out, they were going to be using themselves to do it. And none of that is to mention the passengers the parent comment was referring to, who made the conscious, heroic decision that their plane wasn't going to be used as a weapon like two previous ones had been, whatever the cost.
I don't mean to assume bad faith, but this was, at best, a throwaway comment that minimized the bravery and sacrifice of a lot of good people. Either way, I'd like to recommend you educate yourself a bit more. The Wikipedia page has some excellent detail, and if narrative structure is your thing, the book The Only Plane In The Sky is a masterpiece on the subject.
From the government itself? You can listen to unclassified / declassified 9/11-related communications (all over YouTube) and literally hear the conversations happening. The pilots have done interviews. There’s really no questioning it. It’s part of the US being woefully unprepared for 9/11 because it was so left of field. All evidence points to a lot of brave people doing their absolute best, working within a system that didn’t know how to handle the circumstance. That includes not being prepared to take down a commercial airliner at short notice, because why the hell would anyone ever need to do that!? (no sarcasm intended).
