What does your dad bring with him to prove his identity and what is the process for him to get through security?
As far as I know he has nothing. Perhaps a Medicare card? Though my stepmom is a nurse and therefore probably has super insurance, so he might not have Medicare at all. Insurance card? Maybe SS? Library? He doesn't work anymore so he has no work ID.
You just get the rubber glove treatment. Full luggage search and full body pat-down.
This is not what my father has described in any way, shape, or form. And my brother has flown with him and is more honest than he is, and hasn't described that, either.
Just a lot of talking, from what they've described.
They even left the airport during a layover, on their last flight up to Alaska; checked luggage being moved from one plane to the next, and they felt comfy enough to leave and re-do security in a new airport. Dad carried a briefcase and his two canes (just get the knee replacements, dude), brother had something, they just gave themselves an extra half hour or so from when I would have headed through. Got to Alaska just fine.
Yes my father is bananas. Got angry at the government several years ago when he got a ticket while fighting another ticket, and refused to pay...hence, no ID. But the above is his experience, so I wouldn't freak out too much about this.