I think the gist of the denouement was that he was a good
Captain,he didn't let a poor dead flight attendant take the
fall for him (even if he could have gotten away with it).And
he learned an essential core truth of life-----that even if you
"get away with" whatever it is you've done.....YOU know what
you did.You cannot unknow it, and even if you keep the
secret hermetically sealed & perfectly guarded---it will fester
and rot your soul a thousand times worse than any revelation
could ever do.
Denzel faced the music.Good character beat out the
devil of addiction....decisively, and at the moment of truth!