Originally Posted by
hoshattack
The ticket UA is offering is a round-trip to CDG. I imagine what you're seeing with the LH fare is the doing the open jaw IAD-LHR and CDG-IAD plus a short segment in the middle from LHR to CDG. The short hop from LHR to CDG can only be plated on LH stock now (as an intra-Europe flight) so it's the only way to get this on a single ticket. UA will gladly sell you the IAD-LHR / CDG-IAD portion for just $673, however, if you really wanted to get that part on 016 stock.
Huh? You can't have a single ticket on more than one carrier's stock.
UA is happy to sell the complete itinerary on 016 stock. It just costs more than ticketing through LH because the inventory for CDG-FRA is different native flight number vs. codeshare (S on the UA codeshare vs. K on the native LH flight).