Originally Posted by
JimInOhio
I think the reservations do need to be linked otherwise the originating airline's computer system can't know or see the final destination. That's required to get a bag to that place.
In the past, all that was needed was the destination and the flight number. Today the tracking systems are more robust so requirements may have changed, but the reality is that many airlines these days have stopped checking bags through AT ALL on separate reservations, even if the two reservations are with the same airline.