Originally Posted by Efrem
I'm not sure what you mean by "frequent flyer program codes." There is no official standard set of abbreviations for the names of frequent flyer programs, such as there are for airlines, ...
In the PNR, each FF membership number is prefixed by a 2-letter code signifying the specific FF program where the passenger requests to accrue the miles (the 2-letter code often, if not always, corresponds to the airline which owns the program). In this respect, there
is a code that being used, at least internally within the various CRSs.