I've had the same situation. AA codeshare on IB. Until I selected seats on AA.COM, I had a link that worked. Once selected, the link disappeared and was never to be seen again. It was explained to me that CODESHARE flights are kept in separate system (database?) and only "loaded" into the main IB reservation system a few days before flight. (Hence no meals could be selected either) Who knows if the explanation is correct?. BUT - my selected seats have remained - 5 of 5 so far. But no changes once selected - so "choose wisely!" (Now if IB only offered Champagne prior to take-off! Heck - not even Cava till inflight

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