I've got MOT-MSP-LHR-MSP-MOT booked in Business Elite in about a week's time. The TATL is booked in Z, which I understood to be a discounted business fare.

The fare chart linked off the forum sticky shows Z as a "Business Elite upgrade", so I'm confused about what Z actually means.

A different, and less important, question relates to what might happen if my MOT-MSP leg is cancelled or delayed to the point that the LHR leg is missed (I have 3h 15 in MSP so there should be plenty of time for a delay). I rarely fly DL and have never done so TATL, so I'm unfamiliar with the ins and outs of what is the best thing to do when things go awry (this, after many years as an AC Elite--I had IROPS sorted on them).

Is DL likely to rebook on another carrier if pushed? The only way I can see to get to LON on the scheduled day is to get on one of the daytime flights the next morning (DL doesn't have one, right?) and the MOT-MSP flight I'm on is the last of the day so if that doesn't go I'd have to get on UA to DEN in order to move on that day. I really don't want to have to spend a night in Minot and then wait around in MSP the next day as I've got a bit of a drive down from Canada to get to MOT.