This got me to go find something online and I did find the entire IATA baggage regulation pdf file. There is a lot of truth to what is being said. To summarize - basically, when bag irregularities happen, there is a pro-rate of cost back through the ticket unless blame is clear and then I think it can be 100% charged to the problem station. What was recently agreed now (in 2020) is that in the case of Airline 1 through-checking to Airline 2 where tickets are separate - - in the event of irregularities, there is no pro-rate and Airline 2 can charge Airline 1 all the cost. I suppose within Star-Alliance they will allow through-checks as they have made other agreements within themselves as a customer service initiative.

So - there is truth to the statement that this new and this is a liability issue. It is totally possible to through-check a bag as long as there is a basic existing through-check baggage agreement - however in the case of a problem, the costs will not be split when tickets are separate. It may seem petty - but I guess AC has decided that to avoid uncontrollable charge-backs via BSP/IATA from Airline 2 they have decided just to not allow the this to occur. It also seems to be be somewhat new as this PDF I saw was from 2020.


For those crazy airline geeks - it is a good read - to understand how things work. For now - some quotes from the document.

"Unless subject to specific agreement between airlines, through check-in baggage on separate tickets is prohibited."

"Following the IATA Resolution 754 (Profile 10 - Through Check-in—No Interline Agreement between Carriers), when the originating carrier accepts baggage for through check-in and no interline agreement exists between the carriers, it will be considered as a fault in the baggage prorate process, and will result in 100% prorate of the mishandling expense to the carrier who checked in the bag. "