Originally Posted by sukn

Well, I was just speaking to the EXP about my ZRH trip and decided to ask the agent about our topic at hand. She confirmed that the original booking class has to be available for the downgrade otherwise you will also get charged a fare difference upon the downgrade. This was a Tucson agent with quite a bit of experience and unlike some of the newer agents, knew how to look up the eVIP upgrade waitlist on the old reservation system so FWIW, I tend to believe her.

As for the example of what happen to a PLT who decides on a downgrade at the airport, as we all know TAs and GAs have a quite a bit of latitude and suspect they would downgrade the passenger without much fuss (assuming it isn't a full flight). But this is just an assumption on my part based on my past experiences with TAs and GAs.