First of all, welcome to FlyerTalk. FT is a wonderful resource, and is filled with a great deal of information. I encourage you to take some time to read the various posts on this board. In both the AA and UA forum, you will find several discussions related to this topic.

To partially answer your question, United's frequent flyer program still exists, so accumulated miles can still be used. As many people are saying, it would take a heck of a lot for a bankrupt airline to do away with its' frequent flyer program. And if things came to that point, the only thing to do is to use your miles now. But I, and many others, believe that the AAdvantage program will be here for quite some time.

Again, welcome to FT.