The UK government has come under criticism for committing millions of pounds to a Net Zero initiative aimed at preventing passenger aircraft from producing vapour trails, or contrails, in the sky. Critics have dismissed the scheme as unrealistic, arguing that the funding would be better spent elsewhere, and have warned that the costs associated with the project could ultimately be passed on to consumers through higher air fares.

Contrails form when aircraft engine emissions condense in cold, high-altitude air, and some scientific research suggests they can contribute to atmospheric warming by trapping heat. The scheme reportedly seeks to address this through changes such as altering flight paths or altitudes to avoid conditions that produce contrails, though opponents have branded the approach "pie in the sky" and questioned its practicality and value for money given the scale of investment required.