Xiamen Gaoqi International Airport to Cincinnati Northern Kentucky International Airport
Approx. 12557 km - about 15h 19m in the air and 16h 43m total from gate to gate, at an average speed around 820 km/h.
Real-world flights on routes this long almost always include at least one stop. Use this nonstop estimate as a guide, and allow extra time for connections and layovers when planning your trip.