Originally Posted by
xliioper
TEven though UA website calls these "B" fares, they do not actually appear to be B booking class fares (unless they just book all Economy Plus fares into B booking class) . When I looked up the fare basis codes when I tried it, they were a combination WAA2OFIN and SAA2AFIN fares. The "I" in the second to last character of the fare basis code identifies it as an Economy Plus fare.
They do book into the B booking class. They're dual inventory differential fares that book into B but also check W- and S- availability and use the fare basis codes you note (similar to how TFA2AFFN books into P as a differential fare).