I book most of my flights on co.com, since we seem to be “encouraged” to do so. Booking CLE-GRU, mostly codeshares on United came up. So did CLE-ORD-GRU.

Now I find out that if you book a CO codeshare on ANY Star Alliance flight, including United, you cannot use CO miles to upgrade. Did two calls to CO to ask about this. Oh well, lesson learned (maybe). I guess on previous *Alliance flights, I did book with the other airline directly.

OK, maybe I read the above in FlyerTalk somewhere, but it did not register. Any comments (other than “read the darn rules before booking …")? At least, the seat is E+.