There's only three circumstances where you would:
There is no air brake endorsement - a CDL driver must complete the written air brakes test and conduct their road test in an air brake equipped vehicle, or they will receive a restriction which prohibits them from operating an air brake equipped commercial vehicle.
Air brakes have absolutely NO effect on whether a vehicle requires a CDL or not.
Yes
Air brakes don't determine whether or not a vehicle needs a CDL.
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.
You can get a Class A CDL without air brakes - you'll just have a "no air brakes" restriction which prohibits you from operating a CMV equipped with air brakes. The vehicles you road test have to be commercial vehicles subject to FHWA regulations - recreational vehicles are exempt, so you cannot get a CDL with one.
The braking system doesn't determine whether or not a vehicle requires a CDL.
If the truck and trailer are not equiped with air brakes. If the truck and trailer are not comercial vehicals.
Depends on the gross weight rating. If it's rated at 26,000 lbs. and below (such as a Ford F650 or F750), no, as long as you don't go over that weight. If it's a vehicle rated at over 26,000 lbs, then you need a Class B CDL. Now, if you take a truck rated at 26,000 lbs (which you wouldn't need a CDL for), then add a trailer, you've created a combination with a GVWR of over 26,000 lbs, and you would need a CDL for it. If the trailer is rated under 10,000 lbs., you would need a Class B CDL. If the trailer is rated over 10,000 lbs, you would need a Class A CDL (the same licence you would need to drive an 18 wheeler). So, basically, for a few examples: 26,000 lb. truck with air brakes = No CDL required 30,000 lb. truck with air brakes = Class B CDL with air brakes required 26,000 lb. truck with air brakes and a trailer of less than 10,000 lbs = Class B CDL with air brakes required 26,000 lb. truck with air brakes and 15,000 lb. trailer = Class A CDL with air brakes required 10,000 lb. truck with 15,000 lb. trailer = No CDL required 10,000 lb. truck with 20,000 lb. trailer = Class A CDL required (no air brakes necessary if the vehicle is not so equipped) Bear in mind that these are for gross vehicle weight ratings, not the actual weight of the vehicle itself. So, if a truck weighs 10,000 lbs. empty, but has a gross vehicle weight rating of 33,000 lbs., you need a CDL to operate that vehicle at all times, regardless of what the actual weight of it is at any given time. There is no actual air brake endorsement for CDLs - if you don't pass the written portion of the exam and test in a vehicle equipped with air brakes, you get an L restriction.
You don't need a CDL to operate a vehicle with air brakes if the vehicle doesn't fall within the requirements to mandate a CDL licenced driver to operate it. For example, RVs often have air brakes, as do many of the trucks manufactured for companies like FedEx, UPS, Merita Bread, etc.
You need a valid drivers license. Air brakes don't affect what type of license you need.
There is no such thing as an air brake endorsement on any US license, CDL or otherwise. Only a restriction for CDL holders if they don't complete the written air brakes test and perform their pretrip and road tests in a CMV equipped with air brakes, which prohibits them from operating a vehicle requiring a CDL which is equipped with air brakes.
You can get a free CDL air break practice test at www.testquestionsandanswers.com/cdl/air-brakes-test.html You could also try calling around local truck stops for help.