Originally Posted by
paine445
I also realized that I have a nice run of FRA-MUC-LHR on LH, LHR-YUL-SFO on AC, and SFO-EWR on United. Is it possible to do interlines on THREE carriers?

Star Gold so free bag. Would be one heck of a souvenir bag tag - current record is 4 codes on a tag.
Best asked in the LH forum, but there's nothing technical that would preclude it from working; it would be a policy issue. (It's perfectly possible to craft a three-carrier itinerary, so it's possible to check bags to a third carrier).
I wouldn't do it with a bag whose contents I needed that day in SFO.
Originally Posted by
paine445
Now that I've been thinking about it... there are a lot of *A to *A trips I have coming up on different PNRs, this would be pretty cool - do you have to present both tickets to Agent at origin?
Yes. They'll use your other ticket(s) in order to get your itinerary to print your tag.