I know this is a stupid question and I recall seeing a posting maybe answering a similar question before, but I can't find it again....

Let say I will be taking CO2 from GUM-NHL-IAH. Since it is the same flight #, I know if this is AC flight, I only get mileage calculated as GUM-IAH. But I recall somewhere I have read CO (or UA?) does credit the miles as 2 separate flights... Or am I having faulty memory?

Now to make matter complicated, what if I want to earn AC miles on this CO flight?