The real reason for discrepancies in flight times is jet streams, fast-flowing air currents in the atmosphere. Jet streams are formed by atmospheric heating and the Earth's Coriolis force. They can be as strong as 80 to 140 miles per hour and significantly impact flight times.
Why do flights take longer routes?
Longest passenger flightsThe actual distance flown, however, can be longer than the great-circle distance for a variety of reasons, such as avoiding severe weather, taking advantage of favorable winds aloft, detouring around closed airspace, and diverting around conflict zones.