I've thought about the same route. I think having solid aviation credentials coupled with a CPA cert might be a winning combination in the business aviation world. If a businessman is hiring you directly, not some outsourced personnel dept, it might cause your resume to jump to the top of the stack.

The beauty to the CPA credential is that it is the most widely recognized accounting certification that one can get. There are others out there that could be argued as being tougher, EA, CMA, CIA, etc. Anyone who understands the business world will admit that its no cakewalk to get and it does command a level of respect among business professionals.

In my travels, the CPA is more highly regarded than the MBA. If you can do both, then you have the best combination. However, if you can only do one, I believe the CPA is the best route to go. The reason is that the MBA is just more classes. Most of them are just general business case study type of classes. The CPA is very technical. The focused nature of the CPA, IMHO, puts it higher up the food chain than a general MBA. Not to mention the BIG WHOPPING test at the end. There is no such test besides the GMAT (entrance exam) for an MBA.

Both are awesome on a resume, however. If you have an interest in doing it, I'd recommend it.