Comparing a BAA0AFEN fare with a BAA0AFEN/PC01 fare, there are some differences here and there but what gets my attention most is that the /PC01 requires UA flights and does not allow nonstop flights "THE FARE COMPONENT MUST BE ON ONE OR MORE OF THE FOLLOWING ANY UA FLIGHT OPERATED BY UA BUT NOT ON NONSTOP FLIGHTS." The same fare without the PC01 designator has no restrictions in the flight application.

I also notice that the /PC01 fare comes in 0.16% cheaper in the base fare, which amounts to $1.40 in my example. Not sure if this is done to get the upper hand in some comparison engine, but it may not be a good deal to save $1.40 to lose the ability to book nonstop flights.

[MENTION=52040]lincolnjkc[/MENTION] was the PC01 option also offered for an itinerary with stops in your case?