If the Earth turns east, why isn’t it faster to fly west?

If the Earth rotates eastwards, shouldn’t we arrive at our destination first by moving clockwise?

Even if we don’t notice it, the Earth rotates around its axis from west to east, at a speed of 1,670 km/h at the equator (1,180 km/h at intermediate latitudes), so one might think that, moving westwards, an aeroplane reaches its destination faster, because it somehow meets it, gets closer to it, right?

Wrong: It is exactly the opposite: a plane takes less time if it flies from west to east.

Even the plane, with the ground from which it takes off and like the Earth’s atmosphere in which it flies, is affected by rotation, and therefore moves away from its destination, as it tries to get closer to it.

An aeroplane travelling west does not go faster because, simply, the aeroplane itself is also involved in the Earth’s rotation.

In order for the plane to be able to move actively, it must begin to move relative to the ground, and acquire a speed of at least 160 km/h. If the plane moves east, this little extra speed is added to the 1,670 km/h of before. If it moves westwards, as it is “dragged” in the opposite direction along with the atmosphere, it is as if it is still moving eastwards, minus those 160 km/h. In practice, to go westwards you still move eastwards, and in any case more slowly than the earth’s rotation speed (unless you are at the poles, as you can see in the video).

Coriolis effect

Earth's rotation. Coriolis effect

The Coriolis force (or simply Coriolis effect) is a force triggered by the Earth’s rotation, capable of generating strong jet currents. These currents flow at high speed in the direction of the Earth’s rotation, so at high altitude real air lanes are created, which the aircraft use to reach higher speeds during navigation from west to east.

Conversely, flying from east to west, these currents resist flight, literally pushing the aircraft away from its destination.

Jet Stream

The possibility of using the jet stream to shorten flight times was not immediately obvious. The first airline to realise the usefulness of these strong air currents during navigation was Pan Am in 1952. A Boeing B-377 set a new flight record by completing the Tokyo-Honolulu route in just 11 hours and 30 minutes, instead of the 18 hours previously. The pilot, using the jet stream, even managed to avoid the planned stop for refuelling.