Therefore, if you plan to drive a 24-foot box truck with air brakes in Indiana and the GVWR of the truck or the combined GVWR of the truck and any towed vehicle exceeds 26,000 pounds, you will need a Class B CDL with an air brake endorsement.
It's important to note that state regulations can change over time, so it's always best to check with the Indiana Bureau of Motor Vehicles (BMV) or a qualified CDL training provider for the most up-to-date information and specific requirements.