Climate change could make flights from the UK to the US take longer, according to a new study.
Researchers say global warming is likely to speed up jet stream winds, adding thousands of hours a year to journey times and boosting fuel costs and carbon dioxide (CO2) emissions.
In research published in the journal Environment Research Letters, researchers from the University of Reading used climate models to simulate how a doubling of atmospheric CO2 would affect atmospheric winds.
They then fed that data into a flight routing program, which showed flights from London will become twice as likely to take over seven hours, while flights from New York will speed up and become twice as likely to take under five hours and 20 minutes.
While flights will only gain or lose a few minutes each way on average, the cumulative impact is "significant," the authors write.
"The bad news for passengers is that westbound flights will be battling against stronger headwinds," study leader Paul Williams, an atmospheric scientist at the University of Reading, said in a statement.
"The good news is that eastbound flights will be boosted by stronger tailwinds, but not enough to compensate for the longer westbound journeys. The net result is that roundtrip journeys will significantly lengthen."
Last year, a study led by Mr Williams found flights will b3ecome bumpier as global warming destabilises air currents.