Crediting miles to different programs.
 

I am flying ALB-ATL-MCO and have a Delta SkyMiles Gold Amex. I would like to use the free checked bag perk as well as the expedited boarding on the trip. It appears that to take advantage of this you must buy the ticket w/the AMEX Delta card (done) and make sure your SkyMiles number is in the reservation. This is my problem: I also want to earn credit for at least one segment in AF's flying blue program to prolong my miles for an additional 18 months. Is it possible to use my SkyMiles number when checking in at ALB for the free bag/boarding and later insert my AF number in the record to get mileage for the ATL-MCO segment? Any tips or suggestions would be appreciated.

DL rules say that you must credit the entire itinerary to the same FF program in that you cannot change the FF number after the first segment has been boarded/flown.

"boarded" is after "checked in" ... the gate agent **might** be able to change the number in the record before boarding

You need not pay for the ticket with the Delta Amex card, it only has to be in your Delta Sky Miles profile. You will get the free checked bag, BUT you must include your Sky Miles number in the PNR to get the free bag, so it is a catch 22. As others have said, you cannot change the frequent flyer account in the PNR once travel has commenced.