Yeah its a total PAIN!!! Especially when one of the connecting partner airlines lose/delay bagage!!!

For ex. a few years ago when AirFrance and Continental had codesharing, I flew from Florence to Paris on AF and Paris to Ewr on CO. AF left my bags in Paris, CO counter claimed they were not resposible and I'd have to wait 2 days to get my bags on AF flight. I mentions, well aren't u guys codesharing partners, can't u put my bags on the next CO flight from Paris? They NO!!Anyway I got my bags 3 days later!!

When there's codesharing within connecting flights, it's always the other airlines fault as they always claim!!