Originally Posted by
SamOF
Technically it can happen—they did it for me once when a phone agent issued a friend and I into two PNRs for no reason on an international reservation and we coudn't get economy comfort.
I believe they had to create a new two-passenger PNR, then exchange the old tickets for new ones in the new PNR.
Then they didn't join the PNRs. They simply re-did the entire reservation and ticket, which would have required some overrides if the fare class/codes or award space hadn't been available at the time of the "joining."