I checked with Lorrin Walsh, author of Drive Your Motorhhome Like a Pro, and his information was similar to Mark's. Here's what he said:
"At this time the only state that I know of that requires an air brake endorsement is California, but that is only for motorhomes 40' and you also need a 'Non commercial Class B license.' There are also some restrictions as to where you can drive. I have heard that some other states may follow suit. In most states a 'Personal Drivers License' is all you need to drive any size motorhome. I will throw in a twist though, it is my understanding that some states are requiring CDL's and log books for the people who deliver motorhomes, because they are getting paid to drive them and they then fall under the DOT rules."
In my other research I did see strong recommendations to get training if you plan to drive a vehicle with airbrakes.
Good luck! Enjoy your trip.
Jaimie Hall Bruzenak
{Jaimie is a RTA expert RV Lifestyle columnist and some of her columns can be found here}