It should be but CAI has been operated by a 789 on and off recently. I flew CAI-LHR yesterday, booked 2 months out and it changed from a 788 -> 789 about 1 month ago.

They don't sell F (just left empty) and there weren't enough people in J yesterday for them to push GCH into it. I noticed that people who had already booked the "good seats" in J (3A and 3K) on the 788 were put in 13A and 13K when the aircraft changed (still direct access to aisle but now at the back next to WTP).

I am flying back from LHR - CAI next weekend and the 788 is still showing as operating (ie no substitution this time)