Not necessarily. If the vehicle is under 26,000 lbs. GVWR, and is not used to transport hazardous materials or more than 15 persons (including the driver), a CDL isn't required.
Yes
That depends on which country you live in.
Air brakes have absolutely NO effect on whether a vehicle requires a CDL or not.
Whether a vehicle has air, hydraulic, or air-over-hydraulic brakes has zero determination on the class of license required to operate it.
Air brakes have absolutely no determination on whether or not a vehicle requires a CDL. Zip. Zilch. Nada. Not just in Maryland, but in any state.
The braking system doesn't determine whether or not a vehicle requires a CDL.
If it does not require a CDL to be driven, there are no additional requirements. Such an endorsement does not exist on US licenses.
Air brakes are located in the front of a truck or trailer. There are many parts to an air brake. If you suspect a problem, you need to take your truck to get fixed.
If the truck and trailer are not equiped with air brakes. If the truck and trailer are not comercial vehicals.
Yes. You can drive that vehicle with either a Class B or Class A CDL.
To drive a semi truck, you need a specific driving license that allows you to drive that class of vehicle. As well, as proper education and training such as driver's ed.
If you're in the US, there is no such thing as an air brake endorsement. CDL drivers receive a restriction which prohibits them from operating a commercial motor vehicle equipped with air brakes if they do not pass both the written air brakes test and do their road test in a vehicle equipped with air brakes.