When are you required to have an air brake endorsement or certificate?

Endorsement - if you live in a country which requires it for the operation of air brake equipped vehicles. If you live in the US, air brakes aren't an endorsement - a CDL holder will receive a restriction prohibiting them from operating an air brake equipped CMV if they do not complete the written air brakes test and perform their road test in an air brake equipped vehicle.

Certificate - an ASE certificate for air brakes must be awarded to someone before they can legally make adjustments to or perform maintenance on an air brake system.