hauteboy this is not unusual and I'm beginning to wonder whether it's a problem unique to AA and the Sabre system it uses. Perserverance - and/or a call to the AA RTW desk Stateside (1-800 247 3247) - does pay off.

On my ONE5 I was trying to book a HKG-ICN segment using the BA designator on a flight op by CX. Both AA and BA frontline teams were baffled. AA said that although the flight was in its system, they couldn't book it. BA denied all existence of the flight, despite it appearing in the current version of its online timetable and, subsequently, re-verified with BA reservations.

I took the first route: perseverance. In the end my AA reservation agent tried booking the segment under the BA designator and, hey presto, he got it. He even called BA reservations to verify that the reservation had gained 'OK' status.

It's exhausting having to go down this route, but for some off us using the alternate flight number can make a huge difference for bonus mileage.

NB There are some exceptions whereby a codeshare service may only be used if you are connecting from that airline's service on to the codeshare (eg BA flight # from HKG-AKL may only be used if connecting off a BA flight originating from LON), you should find these restrictions listed in the full version timetable of each of the respective OW carriers.

Hope you and others find the info useful. It's a pain in the a**e to be on the receiving end, as it were