Originally Posted by ATOBTTR

I've had it work both ways. Oddly I had better success for a partner operated flight than I did a DL to DL flight. Same year. I did SEA-LAX on DL, connecting to LAX-BNE on Virgin Australia (separate tickets). In SEA, the DL agent was able to check me in and provide boarding passes for the VA LAX-BNE flight. Later that year, on another international trip, DL was unable to do the same for an SEA-BOS/BOS-AMS-BIO trip, which was DL to DL (well, AMS-BIO was operated by KLM but it was booked as a DL codeshare). While my bag could be tagged through to my destination in Europe during check-in at SEA, the agent was unable to check me in and provide boarding passes for the BOS-AMS-BIO ticket and I had to check-in for the BOS-AMS-BIO portion of the trip on arrival into BOS.