Originally Posted by flyastrojets
I upgraded my SFO-DFW-DCA flights with miles this past Friday. (Thank goodness based upon the madhouse scene at both gates, I don't think I would've cleared). The flights were booked into A as is the norm, but have posted to my account as C class, and I received 125% of the miles.
I have yet another slightly-different data point - I did a miles upgrade on LGA-ORD-LAS last Friday, booked in A as expected, and the miles posted today with the class indicated as F and the 50% COS bonus. I've only seen F and Y for that class indicator (though I've never flown business on a 3-class other than stickers, so I don't know what I'd expect it to show).
On the other hand, when I did miles to AUA in January, the class showed up as Y and we did not get any COS bonus. I guess this is due to the special case of both mileage-upgrade and discount-First booking into A for 2-class domestics. (Wasn't there another letter of the alphabet they could use for that one?)