By Abbas Nazil
Microsoft co-founder Bill Gates is backing efforts to reduce aviation’s contribution to climate change by encouraging airlines to adjust flight paths to prevent heat-trapping condensation trails, a strategy he says could eliminate up to two per cent of global warming at relatively low cost.
The initiative focuses on contrails, the white trails sometimes seen behind aircraft, which can persist for hours, spread across the sky and trap heat in the atmosphere.
In a recent climate commentary, Gates explained that while aircraft emissions from burning jet fuel remain a major environmental concern, persistent contrails also contribute significantly to global warming.
He said preventing these trails from forming could offer a relatively affordable way to reduce aviation’s climate impact while the industry continues developing cleaner fuels and alternative aircraft technologies.
Contrails form when water vapour from aircraft engines encounters atmospheric conditions with suitable temperatures and humidity, freezing around tiny particles into ice crystals.
While many of these trails disappear quickly, some remain in the atmosphere for hours and develop into thin, high-altitude clouds known as cirrus clouds.
These persistent trails can reflect incoming sunlight but also trap heat that would otherwise escape into space, particularly at night, contributing to the warming of the planet.
According to Gates, persistent contrails account for approximately half of aviation’s warming effect, making their prevention an important part of efforts to address the sector’s climate footprint.
He argued that airlines could reduce the formation of warming contrails by making small adjustments to aircraft routes, allowing planes to fly above or below atmospheric zones where the trails are likely to develop.
The approach would build on existing flight-planning practices, in which airlines already modify routes to avoid turbulence and adverse weather conditions.
Gates said avoiding most warming contrails could require adjustments to only about five per cent of flights worldwide.
Although such changes may increase fuel consumption slightly, he estimated that the additional fuel used could average around 0.1 per cent across flights, potentially producing a much smaller climate impact than the warming caused by persistent contrails.
He also suggested that the cost of preventing contrails could be substantially lower than that of reducing emissions through sustainable aviation fuel, which remains an important but relatively expensive option for decarbonising long-distance air travel.
Gates has supported research into the approach through Contrails.org, a non-profit organisation working on scientific research and developing open-source software to help airlines identify atmospheric conditions associated with warming contrails.
The organisation has collaborated with American Airlines and Google Research on more than 100 flights involving contrail-avoidance measures, according to Gates.
It is also working with partners on Operation Blue Skies, a study backed by the United Kingdom government that will examine flight adjustments in the Shanwick airspace off the country’s western coast.
The planned trials are expected to involve air traffic control making route changes to help participating aircraft avoid conditions that could produce persistent contrails.
Gates acknowledged that airlines may need stronger incentives to adopt the strategy widely because the financial benefits are less immediately apparent than those associated with conventional flight planning.
Contrails.org is therefore offering its software free of charge to encourage airlines to incorporate contrail avoidance into their operations.
He also recognised the environmental implications of his own air travel, saying he uses sustainable aviation fuel, supports routes that avoid warming contrails and offsets his family’s aviation emissions.
Meanwhile, the aviation industry continues to explore other ways of reducing its environmental impact, including electric and hybrid aircraft for shorter routes and sustainable aviation fuels for longer journeys.
However, these technologies face challenges, including costs, infrastructure requirements, aircraft weight and the need to maintain stringent safety standards.
Gates said contrail prevention could provide a practical measure while cleaner aviation technologies continue to develop and expand.
The proposal highlights the growing attention being given to non-carbon-dioxide effects of aviation, alongside the sector’s direct greenhouse gas emissions.
Its wider adoption will depend on further research, reliable atmospheric forecasting, cooperation between airlines and air traffic controllers, and evidence that route adjustments can consistently reduce warming without compromising flight safety or operational efficiency.
