Originally Posted by
AeRoSpaceman
Out of curiosity would this be considered IDB?
No; IDB protection only applies if the flight is oversold.
Originally Posted by
fastair
YY designates any IATA airline that flies and participates. A single Y designates a prorate Y fare.
I think that was intentional, the idea being that even a full Y fare (e.g., YUA) represents a discount from the YY fares, which are going away in October.