Originally Posted by
Billy Mumphrey
Replace the EM # you added with you Delta SkyMiles #. Priceline let me add my SkyMiles # during booking, but I plan to contact MU closer to my trip to confirm. You can also get it added at checkin.
From experience, you MUST do it at checkin despite what looks to be succefully changing it earlier. The two times I forgot to do so (despite having early applied the DL SM number online) I had to work with DL to get the credits.
You ahve to go to the physical checkin window anyway, so not a big deal to hand them your DL SM card.