Add Yahoo as a preferred source to see more of our stories on Google. If you took a gander at the sky on Tuesday in southern Ontario, you will have noticed some different kind of clouds that you don't ...

Most of us first spot them as children—the white lines in the blue sky that are the telltale sign of a flight overhead. Contrails are an instant visual reminder of air travel, and a source of much ...

If you've ever stared up at the sky and wondered about the long, white streaks emerging behind airplanes, you're definitely not alone. These ghostly lines are called contrails, short for condensation ...

Long-lived contrails form predominantly not in cloud-free skies, but within already existing ice clouds. This is the conclusion reached by a team of scientists from Forschungszentrum Jülich, the ...