Originally Posted by Apieinthesky

I thought this will work, but just wanted to make sure before I book...

I have this outbound itinerary on hold: STL-ORD, then ORD-DFW-LHR the next day.

The STL-ORD and ORD-DFW legs are booked in coach (full Y, though I don't think it makes any difference here), the DFW-LHR leg is booked in business (I bucket).

My intention is to use a SWU to upgrade all three segments, the domestic segments into 2-class first and the DFW-LHR leg into 3-class first. Concerning the stopover in ORD and the mixed classes, there shouldn't be a problem, right?