Do you need an air brake endorsement to drive a vehicle under 26000 pounds with air brakes in Florida?

Only if it's either designed to transport more than 15 persons (including the driver), or else carrying a quantity of hazardous materials which requires the display of placards under the FMCSR. In both instances, you would need at least a Class C CDL without an air brake restriction (there is no actual air brake endorsement), as well as a passenger endorsement (for a passenger bus) or hazardous materials endorsement.