So tomorrow I'm flying YYZ-ZRH in the midst of a YEG-YYZ-ZRH-DAR itinerary. I was booked in Premium Economy on a 787, and very much looking forward to the experience. It seems that AC has changed equipment to a 767 so of course there is no Y+. I happened upon this by chance. Called the reservation line and got an agent who explained that I would now be in Y. I asked about being seated up front and was informed that wasn't possible, but they did offer to change the booking to Flex and refund the difference. OK, so how much would the refund be? After 15 minutes, I was told there would be no refund because I had got the original ticket for a better price than Flex was now (of course, there was only Latitude showing available). But, no worries, said the agent, with the Flex fare, I would get 100% mileage. Great, I said, with the original booking I was a eligible for 125%. Oops. Change had already been made! After a bit of back and forth, I was booked in Latitude, which gives 125% mileage and the chance for a no-add-on upgrade. Bottom line after an hour on the phone, I am now booked in Y and waitlisted for an upgrade. Question is, what would have happened if I had simply shown up at the airport tomorrow to discover that I had been downgraded?