I've always wondered who takes responsibility for missing connections if the connecting-to-flight was booked on a different PNR and possibly on a different airline and worse still on a different alliance. Suppose one was going from AAA to BBB to CCC. AAA to BBB was on carrier AB while BBB to CCC was on carrier BC. Now imagine that AB delays its flight so much that BC takes off before AB arrives at BBB. Suppose the following scenarios: (1) AB and BC are the same carrier; (2) AB and BC are not the same carrier but they are members of the same alliance; (3) AB and BC do not belong to the same group. And of course we are assuming that the two flights are booked on different PNRs.

The general question I am asking is how do these three scenarios affect one's ability to go from AAA to CCC via BBB, where BBB is merely a connecting point? More specifically (i) Will AB take responsibility for the misconnection and readily try to rebook one for continuing flights to CCC--a question especially pertinent for scenarios (2) and (3). (ii) Or will it simply shrug its shoulders? (iii) Can one work with BC to get to CCC even though AB or weather is to be blamed? If so how much delay will seem reasonable? (iv) When booking multiple PNRs how much time would one like to allow in between connections so that the case for AB to accommodate becomes more compelling.

Thanks!