I have a flight booked with BA which is LAS-ORD-LHR, however the LAS-ORD leg is operated by AA, so this will mean that I have to check in with them rather than BA. However, I was wondering if there is any way I can still get a free seat reservation on the ORD-LHR leg operated by BA, as I know normally you have to be checking in with BA to get the free seat reservation.