I am going to Milan (MXP) next month via LHR. The LHR/MXP segment is on BA metal, sold to me as a BA flight (BA566).

This same flight also has an AA flight number (AA6520). I can see this flight from "Gates and Times", and, if I enter something like 'JFK/MXP' in the booking engine, it will show the AA number for the LHR/MXP segment. However, if I just ask for LHR/MXP on AA, it shows 'no service'.

This matters to me because, since I am not Platinum, I cannot select my seat on BA until 24 hours out.

Any thoughts anyone?