Frontier Airlines has launched a systemwide bonus of double miles on all flights during the month of September. Register before flying using promo code DBLER and you’ll receive double miles on all Frontier Airlines flights when flying on published fare tickets from Sept. 1 through Sept. 30, 2011. The double miles offer includes flights to Costa Rica, which is around 2,400 miles from Denver. Members flying between Denver and Costa Rica can earn 9,600 miles on this route during the promotion. For more information and to register, visit http://insideflyerus.wpengine.com/link/?4997