Republic Airlines (Indianapolis International) parent holding company, Republic Airways Holdings Inc., has announced the closing of the sale of Frontier Airlines (F9, Denver International) to an affiliate of Phoenix-based investment firm, Indigo Partners LLC. Said Indigo's managing partner William A. Franke: “As air travel costs have moved higher, demand has grown for more affordable options and more choices. One key element to Frontier’s future success will be operating as an ultra low cost carrier that offers low fares. This model, coupled with the Frontier touch, will ensure opportunities for the Frontier team, and provide safe and reliable ULCC air service to our communities and beyond as we grow Frontier under this vision.” Effective upon the closing of the sale, David Siegel, CEO and President of Frontier Airlines, resigned from Republic’s Board of Directors. As it stands, Republic now intends to focus its full attention on its core regional jet business and continue to strengthen its relationships with its major airline partners American Airlines (AA, Dallas/Fort Worth), Delta Air Lines (DL, Atlanta Hartsfield Jackson) and United Airlines (UA, Chicago O'Hare).