Just curious - How do the airline / hotel dining programs (Ex. AAdvantage dining, HHonors dining) work behind the scenes? Under any of the programs, you register a specific credit card and then receive air / hotel points when you use that card at a restaurant that participates in the program. How does the purchase information get routed back to the dining program for credit? Do the programs work directly with the Amex, Mastercard, and Visa networks? If you were to register one card to two different programs, would each program give you credit for a single purchase transaction?