You DO NOT need a CDL for an air brake equipped vehicle if:
It is a vehicle with a Gross Vehicle Weight Rating of 26,000 lbs. or less (and is kept under that weight), provided it is not carrying hazardous materials requiring placards to be displayed, nor is it a vehicle designed to carry more than 15 passengers (including the driver)
It is a registered farm vehicle, provided it is operated by the farmer, members of the farmer's immediate family, or direct employees of the farmer, and it is engaged in activities only in support of farm operations, and not used on a for-hire basis
The vehicle is a military vehicle, operated by military personnel (including reservists on drill) in support of military operations
The vehicle is a registered recreational vehicle/motorhome