Originally Posted by
Marathon Man
how can that be? Is not a mile a mile?
Delta "Bonus Miles" do not delay expiration, only "Miles" do . The word "Bonus" seems to be the key.
Virtually every freebie that Delta offers involves Bonus Miles. To get Miles, you need to fly, buy with DL credit card or use Rewards Network. (There may be others also.)
If you check your DL account, you will see Miles and Bonus Miles tallied separately.