Reader Robert wanted to know,
I wish to understand how business class flights booked with Avios points and different One World partners can be put together to form a single itinerary with a common luggage limit. Imagine, for the sake of example, that the longest leg is JFK-MAD on Iberia booked by transferring Avios points to Iberia. The other legs are YYZ-JFK booked on American using Avios points at BA and MAD-LHR booked on BA using Avios points at BA.
While American no longer ‘through checks’ bags to your final destination when traveling on separate tickets, they have an exception when those tickets are on oneworld alliance airlines.
Furthermore, and this is beyond the scope of the question, it’s worth noting that when you’re connecting between American and another oneworld airline, American will treat you as though you’re on a single ticket in the event of irregular operations.
So if you’re redeeming an American flight and then an Iberia flight, whether you’re on one ticket or two, you’re effectively going to be treated on one for baggage and flight protection purposes.
In the case described above it’s no problem to through check bags under the same rules as if this were a single ticket.