Q&A: Why are flights from USA to Europe (Brussels say) shorter than Europe to USA?

by Márcio Cabral de Moura

Question by DateWithDestiny: Why are flights from USA to Europe (Brussels say) shorter than Europe to USA?
I recently observed than flight from chicago to brussels is 7 hrs 50 min and Brussels to chicago is 9 hrs 30 min on the same airline. One thing I have noticed is that the flight takes a different route on its way to the US and does not directly cut through the atlantic to take the shortest straight line path. It goes over iceland, greenland and then comes down south. However, from chicago to europe, they cut right through the atlantic ocean and take more or less the shortest path. I am not able to understand why the different routes on the forward and return journeys?
I recently observed than flight from chicago to brussels is 7 hrs 50 min and Brussels to chicago is 9 hrs 30 min on the same airline. One thing I have noticed is that the flight takes a different route on its way to the US and does not directly cut through the atlantic to take the shortest straight line path. It goes over iceland, greenland and then comes down south. However, from chicago to europe, they cut right through the atlantic ocean and take more or less the shortest path. I am not able to understand why the different routes on the forward and return journeys?

EDIT: Maybe I should have rephrased the question. I was wondering why the longer route towards US and shorter towards Europe? Is there any other reason apart from air traffic?

Best answer:

Answer by The Shadow
Westbound flights are longer because of prevailing winds. A flight from Europe to the US flies into headwinds. A flight from the US to Europe has a tailwind. That has the effect of boosting the aircraft’s speed to Europe and slowing it down on the return.

I disagree with you that eastbound flights cut right across the Atlantic and “take the shortest path”. I’ve flow to Europe more than 20 times and none of them have done that. I also monitor transatlantic air traffic control on shortwave radio, so I know the usual routes.

“Straight across the Atlantic” is not the shortest route. It is the longest. That’s because of the curvature of the earth. Transatlantic flights use “great circle” routes that compensate for the curvature of the earth and are shorter. This will make sense if you look at a globe instead of a flat map. If you take a piece of string and plot the shortest route, it will not be straight line around the globe.

Routes may differ somewhat on the outbound and return. Transatlantic routes are set daily based on weather conditions. There are multiple “tracks” that are used. One flight may be on a more northerly track than a different one. This is done to allow as many flights as possible to cross the ocean while remaining a safe distance apart. Also, each track may have aircraft at different altitudes.

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