I have a Discount Travel E-Cert (PK269). Term and condition 6 on the back states "This E-Cert may not be combined with any other coupon, E-Cert, discount, promotional fare also known as web fare, ticket designator/reference code, bonus, WorldPerks Air Travel Award, group fare, or special status type fares such as: government, standby, military, unpublished companion, VUSA, agency/industry discount, children, free, no-value, unpublished, student, joint, corporate discount, fares filed by rule or any other fares/tickets which may later be specified by NWA with or without notice."