Flight International Airport departs from Muscat International Airport at 23:25 and arrives at Colombo Bandaranaike International Airport at 05:00.
The flighttime is about 4h 05m. The distance travelled ("as the bird flies"): 2466 Km. So the average speed is roughly 604 Km.
There is an 1.5 hour time difference between Muscat and Colombo