Originally Posted by
astroflyer
...One thing that might help is that rebookings are sometimes done in Y which can promote your place in the upgrade queue, but that's a mistake/feature/not always done.
I've almost always rebooked in Y fare class. Even when not a connection, but rebooked on another flight due to IRROPS. Regardless of whether you get your upgrade back, you get the unexpected mileage bonus (if on an M fare or less). That can make up for the loss of cabin.