Originally Posted by
49er
I got the SN PNR by calling United (United.com isn't showing it), but entering the SN PNR on SN's website gives an error. I ended up calling SN and they assigned seats and confirmed that I'm allowed a free checked bag.
Now the only issue is whether I'll be able to check-in online on SN's website, or whether I'll have to check-in at the airport.
You should be able to check in online with the PNR you got for SN. (Or at least that was my experience in December when I did exactly as you are doing).