Originally Posted by
Newfiescreech
I have tried doing exactly that, but with UK-based travel websites, which are in no short supply. The only bad thing about this is that it tends to show discount airlines and non-*A airlines more often than the *A airlines themselves. I agree with you that this method makes more sense and is more useful than using the *A website itself.
None of the travel web sites that I'm aware of allow filtering by airline alliance.
Your best bet is to run two airline-specific searches, one on BD and the other on LH. Those two should find almost all *A flights given their codeshare arrangements, and the percentage of *A LHR landing slots they hold.