Originally Posted by
heliot2009
Only as a reference: I once had IRROPS caused by QR at GRU and lost LA connecting flight. Even though it was a ticket issued by LA and their own flight I missed they refused to fix it and change my ticket. Instead of this they sent me to QR because it was "their fault". Fortunately, I received quick and very professional help from QR agents working at the luggage belts. They changed the ticket accordingly, issued a hotel voucher, etc.
It is the operating carrier causing irregularities on the travel day that is responsible for sorting things out. Sometimes the issuing carrier may take over the ticket once the travel began and it is under airport control, but it’s in very rare situations. I once had a ticket issued on LX stock for OS-operated flights booked under LH codeshare. OS was late causing me to misconnect. Getting to OS counter was a madness line, so I called LX HON team who took over the control of the ticket and rebooked exceptionally due to my status. When I was FTL/SEN, I was always informed that on the travel day the airline that causes irregularity should handle all rebookings.