RDURES - sorry to disagree but CX and AA are are most certainly not on the same res system. what does happen is that once you've booked an itin it is sent to all the airlines on the routing. as such each airline has a record. however if you make a change enroute and the carrier does not forward the changes (at least with AA and CX) it will not update automatically. unfortuantely i know this from experience - on many occasions the airline agents themselves have apolgized and said that they are not on the same systems.