Rico:
Cameraguy did a good job answering all your questions - I'm just chiming in with an opinion...

I'm Silver on CO, and have great success upgrading.

However I fly out of BDL (Hartford), which is a much smaller market. There have been many times where FC had only a couple of folks in it.

Flying out of Chicago, you've got a larger population base, so there are bound to be more competition for the upgrades. I'd be willing to bet that Silvers are not as successful out there.

Another thing to keep in mind is tht you can earn CO status miles flying NW codeshares and vice-versa.

Frankly, NW's service is nowhere near what I've enjoyed on CO.

HOWEVER, Elites on CO are at a bit of a disadvantage upgrading on NW and vice-versa. Frankly, I've never gotten an upgrade on NW without some sort of argument. I've gotten confirmed upgrades and seat assignments on the phone, only to be told at the gate I wasn't.

CO's service is excellent. My boss knows that if I can't fly CO, I'm not travelling.

I hope this helps.

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"I will not be pushed, filed, stamped, indexed, briefed, debriefed or numbered. My life is my own."