Small changes to aircraft flight paths to avoid the atmospheric conditions that create condensation trails – known as contrails – could reduce aviation’s global warming impact by nearly half, a new study suggests.

A study in National Science Review quantified “safe nitrogen boundaries” across 2,847 counties in China. It found that a cross-system management strategy could nearly halve total nitrogen pollution, bring atmospheric emissions within safe limits in most regions, and deliver benefits 2.5 times the investment required. Yet water pollution would remain above safe limits in more than half of the counties, highlighting the need for broader socioeconomic changes.