Originally Posted by Bukhara

The TA is wrong about the BA/PK interline relationship. BA and PK have a two-way agreement so each airline can issue the others' flights on their own stock. BA lists all airline with whom it interlines ->here .

BA will permit bookings to be plated on its stock if either BA has the first international sector or if BA has over 50% of the itinerary. Your itinerary looks like a BA fare so there should be no problem issuing this on BA paper.

I would be surprised if AC/PK didn't also have an interline agreement but this is ultimately irrelevant if BA stock could be used for the whole itinerary.