The easiest way to calculate flying time based on distance is to use one of the available websites, such as Ascent Flight Manager, found at FlightManager.com, or AirplaneManager.com. By inputting departure and arrival cities, type of plane or air speed, and wind conditions, these sites can give fairly accurate information.
The primary information needed is the distance, which the websites calculate from the arrival and departure cities. Unlike when traveling on a highway, there are other factors at play. For example, if someone planning a road trip from San Francisco to Los Angeles knows that the distance is roughly 420 miles and plans on averaging 60 miles per hour, the trip should take about seven hours if driving non-stop.
Actual flying time is also affected by wind speed. If a plane traveling at 100 mph is in dead calm conditions, the plane can cover 100 miles in an hour. A plane with a tailwind of 20 mph covers roughly 120 miles in that same hour. Likewise, a plane with a 20-mph headwind only covers 80 miles.
Using the previous figures for the various wind conditions, a plane on a 200-mile trip makes the flight in two hours. The plane with the tailwind makes the trip in roughly 1.6 hours, and the headwind flight takes 2.5 hours.