I realise you're looking for fares to Europe from the USA, but my example may work for you... I just booked LHR-ORD-DFW round-trip in August for GBP342 all in. All the flights are on UA but using BD flt numbers, W-class, booked on the BD website. The same exact flights using UA flt numbers was GBP654 all in. It may be worth a try. The only thing I'm not sure about is whether I'll get my 1P 100% bonus miles although I'm sure I'll at least get the regular miles and EQMs.