I've found the sme scenario for travel in Sept. UA is $300 more then the BMI codeshare ironically, the fareclass was a W on the BMI flight and an S on the UA. It's a gamble, but I'll buy the BMI one and hope to clear the upgrade at the gate. But conversely, there are many dates where BMI is $300 higher then the UA metal. Go figure, what a kooky business.