Flight Bandaranaike International Airport departs from Colombo Bandaranaike International Airport at 18:20 and arrives at Seoul Incheon International Airport at 06:00.
The flighttime is about 8h 10m. The distance travelled ("as the bird flies"): 5052 Km. So the average speed is roughly 619 Km.
There is an 3.5 hour time difference between Colombo and Seoul