Frontier was founded in February 1994, after Continental Airlines closed its hub at Denver. By July 1994, Frontier had started flights with Boeing 737 airplanes. In 1999, the airline bought Airbus A320 family airplanes. As of 2016, Frontier owns 61 Airbus airplanes. Republic Airways Holdings bought Frontier in 2009. Frontier was later sold to Indigo Partners in 2013. Indigo Partners also owns Spirit Airlines, Since 2015, Frontier and Spirit have been thinking about combining to create one large ultra-low fare airline.