Originally Posted by DLroads

I've done it few times before and keep in mind that not all Y fares are mixable, i.e. You usually can't book one way in M and the other in T. I was usually successful in booking one way M and the other way U (given availablity). You sometimes may need to go from M to B to make the segment 'marry'. Why? don't ask me. But, at least the agents were able to get 'B' to price as 'M'. (some computer glitch that I could not understand).