Some flights out of LAX are moving over to US. From the AA trade web site:
Below is a summary of the AA/US metal swap markets:
Effective for travel on/after the following dates, US will operate US prime and AA*/US flights in these markets:
01 Aug 14: LAX-OKC/PHX
19 Aug 14: LAX-XNA
03 Sep 14: LAX-DEN/IAH
19 Aug 14 - 05 Nov 14: MIA-DTW
Please note: AA flights will exit the above markets on those same dates.
Not all US flights have a BA codeshare yet, so they won't be showing up on BA.com.