Originally Posted by
irishguy28
Even more importantly, they operate an anti-trust immunised "metal-neutral" joint-venture across the Atlantic - including (of course!) ATL-AMS and JFK-EDI. As such, they are effectively a single entity where transatlantic flights are involved.
I am unclear of the relevance of this to the OP's query. You can a fully immunised JV and yet have reservation systems and processes that communicate imperfectly with each other and conversely you can have a plain vanilla interline agreement and yet better coordinated systems and reservation processes.. Having anti-trust immunity does not in itself magically change anything to the reservation processes of the airlines concerned nor does it change the legal relationship between the passenger and those airlines.
They may be regarded as a single entity for certain competition law purposes. That does not make them a single entity operationally.