Do i need a cdl in Illinois to drive an antique fire truck with air brakes to a parade?

Answer 1

Air brakes have absolutely nothing to do with determining if a vehicle requires a CDL or not - gross vehicle weight rating (GVWR) does, however.
If it's a vehicle with a GVWR of more than 26,000 lbs, a CDL is required unless it falls under the criteria to be included under the exemptions for emergency vehicles, farm vehicles, recreational vehicles, or military vehicles. In the case of emergency vehicles, that's only applicable to vehicles operated in the service of an emergency services provider, and by personnel employed that agency, operating the equipment in the course of their duties.