AA certainly can and will do this-- and maybe a bit more even, s.o.p. However what LA did in this case is 100% unacceptable and personally I wouldn't settle for just the difference between the two awards one-way. And, BTW, personally I don't believe LA oversells F-- despite how "practical" it might be. Regardless, the OP got seriously shafted here and should demand-- and is entitled to-- compensation above and beyond the mere difference in miles