Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Flint to Cincinnati as you normally would.
There are currently 3+ open flights from Flint to Cincinnati within the next 7 days for less than $400.
Flint Bishop Airport is FNT and Cincinnati Cinci./N. Kentucky Airport is CVG. These codes are created by the International Air Transport Association (IATA) and airlines use them to identify the departing and arrival airports in the flight routes they service.