Originally Posted by daniellam

The system where the PNR resides is called the "reservations system". It can also be referred to as "reservations mode".

The system that handles check-in is called the "Depature Control System", or "DCS". It can also be referred to as "Airport mode", or "DCS mode". The check-in record is called the "DCS record".

Any changes made in "reservations mode" to a PNR after check-in has opened are normally "pushed" through to the DCS record via the "Additions and Deletions List" or "ADL".

However, changes made to the DCS record in DCS mode (eg. airport upgrades, standbys, seat changes after check-in etc.) are not reflected on the PNR on the reservations side.

OLCI on united.com updates the DCS record.

"My Itineraries" on united.com draws data from the PNR in reservations mode.



This can happen when you do a paid upgrade doing OLCI. The PNR in reservations mode is actually updated with the upgrade flight rebooked to NF or NC after payment is taken before performing check-in in DCS mode.