http://www.publications.parliament.u.../532/53206.htm
I was trying to advise BA of what was going on when UA and LH decided to stiff BA and AA over the Atlantic and codeshare agreements. Still, nobody at BA wanted to listen so they got shafted. It is funny what documents you can encounter on your travels.
So, UA and LH have got a huge hub at FRA for all their transfers and AA and BA have a much smaller number of slots available to them at LHR.
The BCal routes to ATL, Houston and DFW are consigned to LGW for their London operation.
If you want to earn miles on BA and AA, then you could always try the QF programme where no such troubles exist!
Spottie
QF Plat!