Originally Posted by
SunLover
The best guess I can anecdotally piece together: if there is a UA segment involved in the reservation the UA system picks up the partner PNR; if the reservation has partner flights only the UA system does not register the partner PNR. In any case the ticket number is universal.
SL
That's not the case. I've had multi-airline trips booked on UA before, where it gave me some, but not all, of the OAL PNR codes. I've also had OAL-only reservations where it gave me the PNR.
Generally, it just seems that the feature works for some airlines (AC and LH seem to be consistent, but I'm sure someone will tell me of a case where it didn't work for them), and doesn't work for others (never successfully gotten Austrian or Thai).