I think, if the plane was diverted and if it landed intact (two HUGE ifs), the only purpose it can possibly have is as a cruise missile.
Like the plot in Debt of Honor, approaching aircraft from out of CONUS are not “already in the system”, like AA 11 was on 9/11. They have to be accepted, and if they replace a real, expected flight and can spoof the electronic ID, they can get quite close to LAX, JFK, or IAD without causing a scramble.
I do not know if measures have been put in place after 9/11 to prevent a Debt of Honor attack.
Hopefully, there’s wreckage and they find it soon.
I’ve been thinking about that book for the last two days. It’s been awhile since I’ve read it, and I don’t remember the particulars.
But needless to say, as bad as it sounds, I’m in agreement with your last sentence.