I've jumpseated back from lots of places on UA and DL. The key is to find the one check-in agent who actually works for the airline, usually the manager. They will have some semblance of how to do the listing. It took 4 guys in Beijing and it seemed like they were re-typing the communist manifesto onto the keyboard, but they were able to figure it out. Same in Mexico, Singapore, Taiwan, and Europe. Plan B is always a zed ticket. But why pay $100 for something you get for free?