Reserving E+ on a BD codeshare of UA metal
 

I'm booking a trip for October LHR-ORD-LHR, which is coming up at £100 cheaper if booked as a BD codeshare. Only question is, how can I get the E+ seating, if I want to credit the flight to my BD card. If I book on the United website, I can reserve E+ now (since I'm 3P), then switch to BD for mileage at check-in, but how do I do that in this case? Any ideas?

Call. Ask them to put your BD number in the FQTV field and your MP number in the FQTS field. That will let you use your UA status benefits, but credit the flight to BD.

I'm curious as to who to ring. If I ring United, will I be listed, and thus able to give them my MP number and book E+ seats? Then I could give my BMI card at check-in? If I ring BMI, I know they won't know what to do, and they couldn't book me into E+ anyway, no?

Call United. You may need to give them the United flight number (even though you're booked under the codeshare), but they should be able to handle everything. You shouldn't need to do anything special at the gate.

Call UA: you should have a United reservation number associated with it. You can always add the BD number back at the check-in kiosk.