Contrails are formed when exhaust fumes from planes turn into ice crystals
We've all looked up and seen the white lines trailing behind aircraft in the sky.
Known as contrails, these icy clouds contribute to climate change, and scientists have been trying to work out how to stop them.
Now, a £5m UK trial will test whether AI can help, by predicting where warming contrails are likely to form and getting planes to avoid those areas.
It will focus on the Shanwick Oceanic airspace in the eastern half of the North Atlantic corridor which accounts for approximately 5% of global contrail warming.
The 30-month Operation Blue Skies project brings together Google, the UK government, the Met Office, air traffic control provider National Air Traffic Services (NATS) and researchers at the University of Cambridge and Imperial College London.
Contrails – also known as vapour trails – are made when the hot exhaust from aircraft engines meets the cold air at high altitude, creating ice crystals.
Many disappear quickly, but in particularly cold and humid conditions they can persist and spread, forming clouds which trap heat that would otherwise escape from the Earth.
Dr Paul Hodgson, Google's technical lead for the operation, told the BBC's Tech Life programme his five-year-old has a more colourful description for the white lines – "sky graffiti".
"We think that contrail warming is responsible for something like a third of all aviation climate warming," he said.
Dr Hodgson acknowledged there was uncertainty around the precise figure, but said scientists were confident it was "either quite a large problem or a very large problem".
The project also comes as the government backs expansion of UK airports, raising the wider question of whether tech solutions can sufficiently reduce aviation's environmental impact as demand for flying grows.
Google is also one of many big tech companies spending billions on new data centres – the giant, power-hungry banks of computer chips which power AI – which environmentalists are concerned will contribute even more to climate change.
Contrails – or condensation trails – are a regular feature in our skies
The idea behind the trial is that if scientists can predict the areas of the atmosphere where contrails are likely to form, aircraft could avoid them.