But they do have harmful effects https://www.nasa.gov/centers-and-facilities/armstrong/nasa-partners-explore-sustainable-fuels-effects-on-aircraft-contrails/#:

But they do have harmful effects https://www.nasa.gov/centers-and-facilities/armstrong/nasa-partners-explore-sustainable-fuels-effects-on-aircraft-contrails/#:~:text=Those%20contrails%20can%20linger%20in,can%20release%20fewer%20soot%20particles https://www.nasa.gov/centers-and-facilities/armstrong/nasa-p....