Originally Posted by Snoopy
Generally it is the first carrier on the itinerary that issues the ticket, at least that has been my experience....
This is how many online travel agencys work it, like Expedia. However, it should be ticketed on the carrier's ticket stock which either filed the fare, or sells any applicable overwater segments.
Example: UA fare, originating from Europe, allows interlining on *A flights within Europe. Fare filed by UA, overwater segment on UA - supposed to be issued on UA 016 ticket stock. It certainly *can* be issued by the *A carrier providing the interline transportation to the UA gateway city, too.