[11/23/2016 @ 2:05 PM] Only UA fares with 1-stop available now. AA/DLand their alliance partners have all pulled their fares.
Delta and SkyTeam partners have round-trip flights from Dallas (DFW/DAL) to London (LHR/LGW) for $488-$530, with a connection. Flights from December to April 2017. No Christmas. Expect prices to fluctuate.
Note: The days before and after New Years are available at the moment, those will likely sell out first. Try Dec 28, 29, 30 and Jan 04, 05.
Read More Cheap Flights: Dallas to London $488-$511 r/t – Delta + SkyTeam