In August 2017, Allegiant announced a new base would be established at the Indianapolis International Airport. The base began operations in early 2018. In February 2018, Allegiant also announced a new base would be established at the Destin–Fort Walton Beach Airport. In June 2018, Allegiant added another base at McGhee Tyson Airport in Knoxville, Tennessee. In January 2019, Allegiant announced they would be adding another base at Gerald R. Ford International Airport in Grand Rapids, Michigan.
In an effort to focus on regional contract flights for major carriers, Republic Airways Holdings announced in January 2012 its intention to sell or spin off Frontier. On January 26, 2012, Republic Airways Holdings appointed former US Airways and Gate Gourmet CEO David Siegel as President and CEO of Frontier Airlines. Republic also added new senior officers for Frontier's finance and commercial team, among other changes in the executive leadership team. Siegel and other Frontier executives moved to Denver where Frontier is headquartered in order to facilitate management of all aspects of Frontier during its separation process from Republic and continue its transformation into an ultra-low-cost carrier.
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.