There is no linking reservations. There is no linking records. The only thing any airline does is they make a note in the record. So this means someone has to look at your record/reservations for them to do anything. Alot of stuff is done by computer or a real person who spends seconds looking at your reservation so never expect any benefit from a note, link etc in your record. As a previous poster said you may gain more compasion from a gate agent if something goes wrong and they can see the situation without having to hear yak yak yak come out of your mouth. Trust me it sounds like yak yak yak to anyone behind a counter.