Operating hours is simply the total hours that the aircraft is operating, which includes start up, check-out, taxi time, wait time in for take-off clearance, and actual flight time. Operating hours is some amount of time greater than the actual flight time (flight hours), which represents actual time the aircraft spends in the air. The actual ratio of flight hours to operating hours can depend on many factors, such as aircraft type, mission length, arrival/departure airport, etc. You need to analyze the mission profile in order to develop a conversion factor.