In summer 2015, a rash of midair breakdowns drew federal scrutiny. "Before the night was finished on June 25, 2015, five Allegiant flights had been interrupted in four hours, all because different planes had failed in midair," reported the Tampa Bay Times. Since October 2015, the Federal Aviation Administration has kept Allegiant under close supervision. In July 2015, Allegiant Air announced bases would be established at the Asheville Regional Airport and Cincinnati/Northern Kentucky International Airport, becoming the first base at a non-vacation destination.
The initial JetExpress partnership with Mesa ended in January 2004, when Horizon Air was selected to operate the routes. Horizon utilized slightly larger CRJ-700 regional jet aircraft on these routes. In August 2006, Frontier and Horizon ended their partnership. While Frontier was generally pleased with Horizon's operation, the carrier decided that it needed to revisit the agreement and find a provider with additional regional jets to grow the operation. The last of the CRJ-700's was returned to the Horizon Air fleet on November 30, 2007.