Spent considerable time trying to get 3 flights (all IB flight numbers - one on BA metal;2 on AA metal) added to my MMB. Adding manually occasionally worked, but then disappeared again. BAEC tried on at least 3 occasions for me, but without success. Pretty frustrating. In the end, despite all BAEC numbers being in booking, only miles that credited automatically were mine - had to retrospectively claim for the other 8 passengers. Frustrating and time consuming and certainly not seamless.