Delta's discount with AT&T isn't very good: 10% on service, and 20% on phones. I was recently told that there is a Boeing discount available to anyone who operates Boeing equipment (I wonder how AT&T would figure that out). That discount is 25% on service and 50% on equipment. I don't have a FAN number for either discount.
We also get the X plan on Ford products and the Preferred Supplier Discount on GM products. (Not that you can't get a great deal on one of those cars anyway).