I was sitting next to a banker who worked for the airlines a couple of years back, and he told me that hording miles was not the best idea.

FF miles are treated as liabilities on the balance sheets. They are an obligation for the airline to repay as the customer demands. In a bankruptcy, all liabilities are subject to risk just as if you had loaned money to the airline.

Thinking back, I believe American honored all of the miles from TWA, just like Delta honored all the miles from Pan Am. So, while there probably is no risk to the AAdvantage miles you are holding, we should all understand that there is a degree of risk should the airline seek chapter 11 protection.