Just clarification here. Unless different from LH, which also owns Austrian, it's. Its not about booking through United (or really, being on an 016 ticket), but whether you are booked on the flight on an Austrian flight number vs. UA codeshare, and whether or not you can assign a seat for free, or need to pay. If you can get a seat for free, flight number shouldn't matter. If you need to pay, the marketing flight does matter.
Im leaving next week on a ticket booked through the UA website, so 016 ticket, with a segment on LH. Initially, it was booked as the UA codeshare, because I couldn't force it to book he LH flight number, but I called within 24 hours, and and agent changed it for me no problem to the LH flight number. This was a W fare, so required a $35 payment for a seat assignment (FRA-BLR). LH website wouldn't let me do it, but called LH and they let me pay for the seat, and gave it to me, no issues. My wife, flying with LH last week - same thing, except her booking already had her on the LH flight number. Again, couldn't do it on the LH site, but was able to call and pay for the seat.
im assuming you are on a W or lower fare, which means you need to pay for a seat in advance. Your only hope to get this prior to check in is to call UA and see if they will change your OS flight to the OS flight number. If you purchased your ticket longer than 24 hours ago, doing that without a change fee would be a huge favor, but it's worth a shot. If they do that, then you should be able to call and buy a seat assignment. If not, you're no worse for than you are now.
I have 2 codeshare flights booked through United, one with Lufthansa (FRA-KRK) and one with Brussels Airlines (TLS-BRU). Last time I flew on Lufthansa with a codeshare with United, I couldn't get a seat assignment when I checked in for my flight with United online or at the airport. I had to wait until my connecting airport (can't remember if we could get it in ORD or had to wait until FRA). I couldn't get the boarding passes either.
However, when I checked my reservation on United's website, it conveniently includes the PNR for Lufthansa and Brussels Airlines. Can I check in again with those websites after I check in with United and move my seat? Or access my reservation within 23-24 hrs and move the seat before I check in with United?
These are fairly short flights and I'm traveling alone, so it's not a huge deal where I sit, but my daughter and I were split up on the previous flight, so I just wondered if this would work. Besides, I'd rather not have a middle seat if I can avoid it, even on a short flight.
While I'm at it, when I do bag drop/print boarding passes at TLS, would that be with Brussels Airlines? I think it's with the operating carrier, but I can't remember for sure. Also, will I be able to print all my boarding passes at TLS, or will I need to wait for BRU for the United ones?
Thanks for any information.