First of all, I want to credit this find to FlyerTalk's thread that got me to this experience write-up. Recently, I was able to grab a Delta airline's economy seat to the U.S. Virgin Islands using Air France's Flying Blue miles. Provided that the seat is in economy class, I may not be able to check bags for free or board the plane faster than the general boarding. However, I am a Delta SkyMiles Business Credit Card holder, and the card gives card member the two benefits that I just mentioned.
  • First checked bag free on Delta flights.
  • Priority boarding on Delta flights. 

You see when it comes to award travels using an airline's miles program to redeem for flights that don't belong to that airline can be a little bit tricky. In this case, I use Air France's Flying Blue to redeem Delta operated flights. So I booked directly with Air France and Air France automatically put my Air France's frequent flyer program's (Flying Blue) number on the confirmed reservation. So Delta will not be able to see that I am a Delta SkyMiles member. To get the benefits from the Delta's credit card, Delta requires that the card member's SkyMiles number is on the reservation. Card member is not required to purchase the ticket directly with Delta or purchase the ticket with the Delta's credit card.

Long story short, I went on Delta website and signed into my SkyMiles account. On My Trips page, I used the trip finder to find my reservation based on the confirmation number. Fortunately, both Air France and Delta have the same confirmation number, so that saved me from searching for that. Once the reservation was loaded, I could view the details of the trip and as I scrolled down until the Passenger Information section, there's a section under my name that allowed me to delete the Air France's frequent flyer number and put in my Delta SkyMiles number instead. That was pretty easy enough and I did not have to call Delta or Air France to accomplish this. Furthermore, now that my SkyMiles number is in the record, that reservation now also shows up on My Trips page so I no longer have to enter the confirmation number each time to look up that reservation.


Bottom Line
The bottom line is, if you use a partner airline's miles to redeem for Delta flights and you hold the American Express Delta Credit Card that give you all the benefits, you can still get all those benefits by simply go to Delta website, view the reservation, and input your SkyMiles number in the reservation online on your own.