Allegiant Air will launch one new year-round and four seasonal routes this June.
The Las Vegas-based carrier will begin seasonal flights between Jacksonville and Louisville, and between Kansas City and Myrtle Beach on 8 June.
On 14 June, it will launch year-round service between Nashville and St Petersburg-Clearwater, as well as seasonal service between Nashville and Syracuse and between Jacksonville and Norfolk.
All routes will be operated twice weekly, says the ultra low-cost carrier.
Allegiant will face no direct competition on any of the routes, FlightGlobal schedules data shows. However, Southwest operates between Nashville and Tampa, which is a bigger alternative airport to St Petersburg-Clearwater.
Among the planned new routes, a number of cities are relatively new to Allegiant's network. Louisville was added in May 2017, while Norfolk came on board in November 2017. Allegiant announced in March the addition of Nashville which joins the airline's network in June.