Originally Posted by
FrancisA
If it were possible to book a BA or IB fare on any IAG airline without any requirement for another flight, that would address the OP’s point. IAG could restrict that to routes not served by its legacy carriers, but I’d have to say if it were a separate fare why do this. Indeed what business reason prevents IAG doing precisely this?
In some cases there are legal issues around this. You cannot offer a codeshare without the approval of both countries on the route. Within Europe that’s no problem, but for instance you could not set up an Iberia codeshare on BA’s LON-MOW without the approval of the Russian government. In some cases that may require a change to the relevant air services treaty at a governmental level.