Two new promotions allow Diners Club Club Rewards members to earn discounts on either American Airlines or United Airlines.

Club Rewards members who use their Diners Card to purchase one roundtrip economy ticket on United or United Express online at http://www.united.com can save 15 percent off eligible fares when using the certificate number listed in their newsletter. Tickets must be purchased by Aug. 7 for travel through Nov. 15. Eligible economy booking classes include H, Q and V. Travel may originate in the United States, Puerto Rico or the U.S. Virgin Islands and destinations include anywhere in the origination zone or Canada.

American AAdvantage is offering a similar promotion, but the discount is a less lucrative five percent. However, the AAdvantage discount is good on more than a single ticket and the eligible fare classes and destinations are far more extensive. Be sure to enter promotion code DCAA when buying your American Airlines or American Eagle ticket online at http://www.aa.com, as the discount cannot be earned retroactively. The eligible fare classes include P. F, A, J, D, Y, B, H, K, M, Q, V, N and L. Tickets must be purchased by Aug. 1 for travel through Nov. 20 within the United States (including Alaska and Hawaii) and from the United States to the Caribbean, Europe and Mexico.