Delta: 15% off award flights with co-brand cards

Delta has added a unique twist to its loyalty program with a 15% discount on the points needed for an award flight when the taxes and fees are paid with a Delta-branded American Express card.

The savings could be considerable: A sample search for flights from New York to Paris, for example, shows savings of 10,000 to 20,000 in Economy or Comfort+, and as much as 110,000 in Delta One premium seats. The discount offer appears automatically when searching while logged in to Delta's website or app.

There are some restrictions, however. The discount applies to all but one co-branded card, the no-fee Blue card. Booking must be done by the primary cardholder, and the benefit can't be used for upgrades and extras added later. It also can't be used on flights operated by other carriers, or if if the purchase uses Delta's Pay with Miles or Miles + Cash programs.