Thought I'd update this thread. I had my flight last week on the UA codeshare, 3M operated flight, EYW-RSW connecting to UA in RSW and going on.

My experience was similar to UA_Flyer above, but their thread isn't coming up anymore for some reason though I recall reading it when initially posted.

This was an e-ticket that included 1 free bag per passenger up to 50 lbs (without any elite benefits) because it originated in Japan. By DOT rules now that sticks to the entire itinerary regardless of stopovers or codeshares down the line.

When I got to the Silver Airways counter in Key West, the lady was quite gruff about it. First one bag was 58 lbs, so she was very quick to say "This isn't United, I see you have elite status here but our rules are only 50 lbs or you have to pay $150 (or some high fee around there)". Fine, I had my 20" roller carry on inside which I just removed and gate checked. Now the weight is fine. Next issue, she says it's $50 for the two bags (1 per pax). I said we're not supposed to pay it. Again she would only robot repeat the line "This isn't United, your elite status is no good here". I explained this has nothing to do with my status on United but this is a DOT rule based on the terms of my e-ticket. She wasn't having any of it, absolutely refused to budge. Called UA Premier line, they said pay it and request a refund from UA when I get home. Fine, I pay. Then I ask if she'll throw my priority tags in the middle of the bag tags so when UA picks them up they come out with the priority bags at my final destination (most non-alliance airlines don't mind doing this). She calls a supervisor saying she wasn't going to be the one to get fired if they aren't allowed... supervisor says it's fine, go ahead. So it would seem that they carry a pretty big chip on their shoulders about the former relationship with UA as an Express carrier and are awfully proud now to be independent and try to charge every ancillary fee they can.

Well, needless to say once I hit the ground in Fort Myers, during my layover I went to the DOT Air Consumer complaint page and filed my complaint with them as Silver broke the rules. I also copied the same email to Silver Customer Service advising them that I've complained to the DOT and that I'd appreciate a refund for the fee they wrongly extorted from me.

I got a reply from the DOT within hours saying that it appears that Silver broke the rules and they were going to move further with an official investigation. I didn't get anything from Silver for several days, however finally they got back to me, apologized and said I'm entitled to a refund of the $50 but I have to call them with my credit card info (a bit inconvenient since I'm 13 hours ahead of them and they're only open 9-5).

Anyone else who encounters this, if your e-ticket allows free baggage then Silver is obliged to honor that and it may take some pushing and supervisor intervention to make it happen. I hope now that they will at least make the outstations aware of this rule.