I would wear a suit, bring logbooks, paperwork, etc and be prepared for a technical and HR interview. Check out their website and certainly follow any instructions regarding the group interviews. Airline recruiters like people who can follow instructions without making excuses.

Usually they do a presentation, written tests, and maybe a mini-interview but in some cases they have conducted the full interview minus the sim. Be prepared to make a good impression, you will likely get invited to SLC for the real interview.