I managed to get a few status matches (bmi, saa, co), but I'm confused about one thing: If I'm status matched on, for example, BMI, I want to utilize their elite benefits. However, I don't want to accumulate miles with them (I'd rather earn with UA or CO). Is that possible?

I know United has two ff fields - an elite ff# and a earning ff#, allowing one to do both But what do you do with other airlines? For example, looks like I'm getting a status match on South African Airways to use on an ORD-JNB trip -- the elite status would be great for possible upgrades, but I'd rather earn UA miles for the long flight.

Do you just ask to change the ff# back at the gate after checking in? (But then it seems you risk losing the possible last-minute upgrade)

I never quite understood how people do this. Thanks for any suggestions.