Frontier Miles is Frontier Airlines' loyalty program. Over the past few years, significant improvements have allowed them to compete head-to-head with fellow low-cost carriers Spirit Airlines and Allegiant Airlines, becoming popular among budget-minded travelers. On Thursday, January 11, Denver-based low-cost carrier Frontier Airlines announced that changes to its Frontier Miles loyalty program are live. Many alterations to the program are being introduced – all of which are beneficial for members.