Originally Posted by jerry a. laska

The tool will probably issue with BA as the ticketing carrier for first segment CAI-LHR, the trouble with that usually is that BA will add fuel surcharges to all segments even if not on BA. If you issue with AA as the ticketing carrier, they will pass on other airlines fuel surcharges but only on segments operated by that other airline. See, e.g. the discussion here:
http://www.flyertalk.com/forum/onewo...correctly.html
There are other threads in the oneworld forum discussing routings and other relevant issues.