The big job fairs mentioned above will hardly give one much time to form a "good relationship" with an HR rep. Under 5 minutes with a screener, perhaps. Maybe a chance to shake Capt Kraby's or Capt Flanagan's hand.

Job fairs won't get "points" at DAL, but WILL get an app scored. Getting a DAL pilot to send one's name in to the hiring desk will do the same thing.

If the fair is worth it for you for other reasons mentioned (or for other airlines who may give special consideration), go for it.

...All that said, I think most of the pilots in my DAL interview class did at least one job fair. I didn't, and managed to get called for the big show anyhow.

But I'm just an anecdote... I didn't do formal interview prep either, and that's definitely not something I'd personally recommend skipping.