Allegiant Air

Allegiant Air is a low-cost, no frills airline offering only direct flights, which out of Cincinnati/Northern Kentucky (CVG) include Phoenix, AZ and several cities in Florida.  You have to be very flexible on dates since they don't fly every day, pay for any extras and willing, in some cases, to fly into lesser-used airports, for example, Punta Gorda instead of Fort Myers.  But the combination of direct (what's 5-6 more hours of vacation worth?) and low cost seems pretty compelling to me.

https://www.allegiantair.com/