Flights will become bumpier as global warming destabilises air at altitudes used by airliners, climate scientists warned.
Turbulence has already injured hundreds of passengers a year, some fatally, and the damage to aircraft cost the industry an estimated US$150 million, scientists said.
"Climate change is not just warming the earth's surface, it is also changing the atmospheric winds 10 kilometres high, where planes fly," said study co-author Paul Williams of the University of Reading's National Centre for Atmospheric Science in England. "That is making the atmosphere more vulnerable to the instability that creates clear-air turbulence. Our research suggests that we'll be seeing the 'fasten seatbelts' sign turned on more often in the decades ahead."
Turbulence is mainly caused by vertical airflow - updraughts and downdraughts - near clouds and thunderstorms.
The authors used supercomputer simulations of the North Atlantic jet stream, the strong upper-atmospheric wind driven by temperature differences between Arctic and tropical air.
The stream affects traffic in the aviation corridor between Europe and North America - one of the world's busiest, with about 300 eastbound and 300 westbound flights per day.
They found that a doubling of carbon dioxide in the atmosphere from pre-industrial levels, predicted within 40 years, would cause turbulence to be 10 per cent to 40 per cent more forceful at typical cruising altitudes.
"Turbulence strong enough to make walking difficult and to dislodge unsecured objects is likely to become twice as common in transatlantic airspace by the middle of this century," Williams said.
"This could also increase the risk of injury to passengers and crew", especially in winter, when northern hemisphere clear-air turbulence is thought to be most intense, he added.