Airframe and Powerplant. In the AF, crew chiefs basically learn how to identify problems, and who to call to fix them. There's sheet metal specialists to do sheetmetal work, jet mechs to fix engines, avionics guys to do avionics, NDI to do detail inspections for cracks and whatnot, fuels specialists to work on fuel systems, corrosion control to paint them, and weapons guys (like I was) to work on the weapon systems. Then there are crew chiefs that make sure all of that work is coordinated and done when it's supposed to be. Unfortunately AF aircraft maintenance is highly specialized, although some of the guys are getting a little more diverse training than they used to. For instance, sheetmetal, welding, and machine shops used to all be in the same building but all seperate career fields. They are now more integrated.

I digress....An A&P license will be a huge boost in helping an AF crew chief get a job working on commercial aircraft on the outside.