-i fly on mu and cz weekly, and always provide my Delta ffp # at check-in
-but, half of the time, I end up earning ZERO miles
-if I were to credit towards mu or cz, I would earn a small pittance of points in half of these "no DL miles" cases
-alternatively, I could spend an extra $75 per flight in order to earn full miles....a poor value proposition IMO, and this is out of pocket
-asia miles includes CA (in addition to MU), but is a bad ffp, and only semi-expensive tickets earn points