Pittsburgh has also been successful in attracting ultra low-cost airlines to the region. Allegiant Air commenced service in February 2015 and has been expanding ever since, establishing a base of operations in Pittsburgh on December 24, 2015, and serving nine destinations as of December 2016. Frontier Airlines also began service to five destinations in June 2016, although service was cut back to three destinations just four months later. Spirit Airlines commenced service to seven destinations between May 2017 and July 2017.