The plot thickens. Monday has come and gone with no cancellation notice, but all BA flights between Dulles and LHR around that date are no longer bookable, except BA216 on 12/26. I'm also seeing lots of zeroed out flights ex BOS, ORD, and JFK on and around 12/26. (i.e., all JFK-LHR flights are zeroed out on 12/24, 27, and 28.)