Originally Posted by
mnbp
The necessary passport prompt only happens at kiosk check-in for an international flight. At your next international flight, check in at an airport kiosk and pay close attention to the prompt message that appears after you scan your passport. You have to say "yes" to the question "Do you want Delta to save your passport details in your Delta profile" or words to that effect. That "yes" choice is the action that "verifies" your passport in your Delta profile.
This - I had to do the same thing a while back at the kiosk and since then my passport is 'verified'.
I was able to do it for a domestic flight at the time however, so maybe that changed a little since a couple years ago.