I'm not usually one to complain as stuff happens, but this really surprised me.

Flew BOS-JFK-DUS this weekend with the first leg on American and the second booked on American and operated by Air Berlin. I had a confirmed preferred coach seat on the Air Berlin flight with plenty of legroom.

Check in online with American and it won't check in my codeshare leg. Ok, go to Air Berlin and try and check in with that PNR and it tells me to check in with American.

Call American and they say I get the second bording pass in BOS. Get to BOS and the desk agent says I have to get the Air Berlin boarding pass at JFK as that's how it works.

Get to JFK to find I forfeited my premium seat because I didn't check in!

Is this a common problem with OW codeshare flights? My bigger gripe is that everyone kept giving me bad info and then I have to suffer for it. I'm tall and the flight was miserable.

My return was bought as AA and operated by BA so I'm assuming this won't be an issue as their systems seem to be more integrated.