Flight Incheon International Airport departs from Seoul Incheon International Airport at 08:10 and arrives at Kathmandu Tribhuvan International Airport at 22:00.The flight has a short stop at Hong Kong.
The flighttime is about 16h 50m. The distance travelled ("as the bird flies"): 4562 Km. So the average speed is roughly 271 Km.
There is an 3 hour time difference between Seoul and Kathmandu