I have just tried to book a return from LAS to NCL for June. Two separate routings:

LAS - PHX - JFK - LHR - NCL - LHR - LAS (Booking classes A,A,I,J,J,T) which BA cannot price in spite of a $4150 price on Matrix

LAS - PHX - PHL - LHR - NCL - LHR - LAS (Booking classes A,A,I,J,J,T) which BA can price at $4150

Both fares show as the same IHX8S3E3 fare rules so I am not sure why I can't get a price for the first. BA say it's because the I class on the JFK - LHR sector can't be combined with the A class on the domestic US flights, but it can obviously be combined with the I class on the PHL - LHR sector.

Outward travel is 23rd June, return on 27th if anyone on here can shed any light?

Also, when I asked the agent to try using the AA codeshare for the JFK - LHR flight, I was told that they can no longer price BA operated flights using the AA or IB codeshare flight numbers - it has to be the BA flight number. This is apparently a new directive from management to explicitly clarify what was apparently a policy more honoured in the breach than the observance before. Wrists have been slapped from what I was told.