Originally Posted by
irishguy28
No; not all BA flights have an AA codeshare.
Bear in mind that such flights can usually only be booked in conjunction with another flight; you can't easily book MAN-LHR on an AA codeshare, for example, unless you have other flights on the same booking that would make the inclusion of/need for such a codeshare "meaningful".
Exactly. Feeder flights to BA long haul airports often have code shares like the IAH-MIA I'm on right now.