The Jet Stream Also Plays a Role
There is another major factor hiding high above the Atlantic:
The jet stream.
The jet stream is a band of very strong winds in the upper atmosphere. In the North Atlantic, these winds generally flow from west to east.
That means an eastbound aircraft can sometimes benefit from strong tailwinds, while a westbound aircraft may face stronger headwinds.
Modern flight planners monitor these winds and adjust routes and altitudes to reduce travel time and fuel consumption. Research published in Atmospheric Chemistry and Physics notes that the North Atlantic jet stream is a major factor in transatlantic flight times and that airlines optimize routes using weather forecasts.
So the route a plane takes across the Atlantic isn’t necessarily the shortest line on a map.
It is often the most efficient route under the current conditions.
