Flights from Britain to the US could take longer in future because of climate change. The jet stream is expected to become more powerful as the climate warms, and that means flights to America battling against fiercer headwinds.

Flights from New York to London, on the other hand, will probably speed up as they ride on the faster jet stream, although this won’t balance the slower flights and a round trip will still be longer. That means more fuel used by the aircraft, more air pollution and possibly higher fares, according to researchers at the University of Reading in a study published in the journal “Environmental Research Letters”.

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And the effect of a powerful jet stream was brought home in a remarkable flight in January last year, when a British Airways flight from New York to London reached 745mph, near supersonic speed, by riding on an exceptionally fast jet stream of around 250mph.

Airlines face other troubles as the climate warms. Planes taking off in hot weather need to reach higher speeds, because warm air is less dense than cold air. That means aircraft having to travel lighter, with fewer passengers or less cargo. Since 1980, the number of flights forced to cut their loads increased at four airports studied in the US, as average temperatures rose at each location.

Alternatively, aircraft will have to use more fuel, but either way it’s likely to mean higher fares. The only other options are more take-offs at night, early mornings or evenings when it’s usually cooler, or building longer runways, none of which is good news.