Skybus Airlines Inc. was a privately held airline based in Columbus, Ohio, United States. It operated as an low-cost carrier modeled after the European airline Ryanair, and aimed to be the least expensive airline in the United States. The business model was heavily reliant on flying routes where other airlines did not have direct flights, as Ryanair did in Europe, thus keeping competition to a minimum, and on flying into secondary airports, rather than heavily trafficked ones. The airline also sold advertising space on the interior and exterior of its aircraft, as well as selling merchandise on board. Skybus applied for operating approval on January 1, 2005, received approval to operate on March 15, 2006, and FAA certification on May 10, 2007. It had been granted a waiver to begin ticket sales on April 24, 2007; Skybus' first passenger flights out of Columbus began on May 22, 2007. Less than a year later, Skybus announced on April 4, 2008, that it would cease operations as of April 5, citing the lagging economy and rising fuel costs as causes.