It has happened to all Travel, and it will surely happen to you too. You booked a return flight, and when you checked the mother daughter trips details, you noticed that the outward and return flights had different durations, despite following the exact same route.
If you thought it was a website error or a special circumstance, we have an explanation for you: an aircraft can take different times to fly the same route in opposite directions.
Let’s take a concrete example: a Ryanair plane leaving Warsaw for Paris takes 1 hour and 55 minutes to complete its flight; on the way back, the same Ryanair plane will leave Paris and arrive in Warsaw after “only” 1 hour and 40 minutes. But how is this possible?
The same airline, the same type of aircraft, the same distance and yet different flight times? The reason is due to the rotation of the earth but wait: do not jump to conclusions! It’s a bit more complicated than it looks.
The Earth rotates in an easterly direction (at 1670 km/h). So, you would think that by moving west, a plane would reach its destination faster, because it would somehow meet it, get closer to it, right? Well, that’s wrong!
In the example above, the Paris-Warsaw route is the shortest in terms of time for a travel blogger, not the other way around, and Paris is the westernmost city, while Warsaw is much further east.
Jetstream: how does it work?
When the Earth rotates, the ground rotates, as does the air, and so the plane is affected. The plane is thus pushed towards the east at a speed much higher than that which it can reach.
The air distance between the airports of Paris and Warsaw is approximately 1366 km. In case of longer flights, the time difference on the same route in opposite directions would increase. So, it has nothing to do with rotation? It does, but not directly.
Don’t worry, if you do some research. You will find that the cause of this unusual jet lag is the Coriolis force. The Coriolis force (or simply the Coriolis effect) is a force triggered by the rotation of the Earth. Which can direct powerful jet streams eastward (between 8 and 12 kilometers in altitude). Generated by the collision of cold air masses in the high latitudes. Closer to the poles – with warmer air masses in the middle latitudes.
These currents flow at high speed in the direction of the Earth’s rotation, creating high-altitude air corridors, which aircraft use to reach higher speeds when flying west to east. Conversely, when flying from east to west, these currents oppose the flight, literally pushing the plane away from its destination.
Discovery of the jet stream
The possibility of exploiting the jet stream (or upper current) to reduce the duration of flights was not immediately obvious. The first airline to realize the usefulness of these strong air currents during navigation was Pan Am in 1952. A Boeing B-377 set a new flight record, completing the Tokyo-Honolulu trip in just 11 hours. And 30 minutes, instead of the 18 hours it had taken before.
The pilot, using the jet stream, even managed to avoid a scheduled refueling stop. Today, these wind highways are considered when planning flight routes. Which is why you can find time differences between outbound and inbound flights in your flight details.