Originally Posted by
Guy Betsy
Its very specifically BA's GDS only. QF doesn't have this problem and it uses AMADEUS, and neither does LH. Actually, no, LH sometimes has this problem too. But so far, neither SQ or CX has this particular issue and they can change FFPs one segment at a time. (All mentioned above use AMADEUS as their GDS). But for BA's it seems that it must be changed BEFORE check in. Apparently once the airline checks you in, and even though you haven't yourself, nothing can be changed beyond that. Something I might try to do before my flight from HKG to LHR this weekend.
GDS =/= reservation system =/= inventory system. BA, LH, CX and hundreds of other airlines use Amadeus as GDS (Global Distribution System), 100+ as reservation system, tens of airlines as inventory system (IIRC). You don't need to be Amadeus hosted to use Amadeus GDS (e.g. Emirates).
What you describe has probably more to do with DCS (Departure Control System) and its processes linked to inventory, if it is not possible to change the FFP after check-in. And that's other system too. On the top of that the agent could be doing the FFP changes in DCS or in reservation system (depending on creativity and access level).
So it's impossible to tell what is happening without knowing more
