Been checking the mobile app daily in the hopes one of my segments between London and New York will get the new aircraft. Checked today and was shocked! Flying back LHr to JFK on 12/25 in Upper Class and now shows as 351 for my flight...137! Already called and got allocated a pair of middle seats for me and the misses. Still no seat map on the mobile app. Now just hope my outbound on 12/11 gets the switch from the 789!