There are differences in Chapter 7, Chapter 11 and Chapter 13 bankruptcies.
Bankruptcy is a general term used to described various bankruptcy provisions.
PMUA and PMCO have declared Chapter 11 multiple times including post 9/11.
Having flown and accumulated miles since late 80s, I have not lost one single miles through bankruptcy, including when Pan Am closed for business. Delta honored all my Pan Am miles without any issues.