Originally Posted by
father_ted
You are probably correct in so far as that is what the airlines want... but there are definitely occasional interesting cases where it is cheaper to buy one carrier's flight on another carrier's code. I think MK/EK to MRU used be one of them.
MK ticket on EK metal to MRU saved me 30% on F fares last September - only MK miles earned and not EK miles other than that all benefits same.