OA: Operations Agent as noted above. This is the person that scans the BP but does a lot of other stuff related to operations. They check in crew, take care of preboards, hand off UM's (Unaccompanied Minors), make boarding announcements and other stuff.

GA: Gate Agent. The person at the desk that answers questions, gives out the blue sleeves, issues BP's for people that need them, tries to reschedule people during IROPS (Irregular Operations), overcharges people wanting to fly standby if their flight is not delayed and issuing C BP's to those that are really delayed, among other things.

SA: Secret Agent. (Cue music.....) "He's a man that leads a life of danger, every one he meets he stays a stranger, whatever move he makes, another chance he takes, odds are he won't live to see tomorrow." Johnny Rivers, 1966. (Did the lyrics from memory.)