Originally Posted by DH
In order to receive Midwest miles for AA flights, use Midwest FF number whenever you take the AA flights. (and use AA FF number for Midwest flights if want the AA miles).
Oddly, while you can earn Midwest miles on YX
or AA, you can earn AA miles
only on AA -- not on YX. Don't know why this is, but have checked with both FF departments, and that is the case.