We see contrails every day in the Boulder skies. Colored like clouds, they are the straight lines in the sky that trail jet planes. And what are they? Why do they appear at all? Some of the Most Interesting Contrails I’ve Seen       pic Lensworth Contrails, short for “condensation trails,” are cloud-like trails left behind by aircraft as they fly through the sky. These are a specific type of cirrus cloud formed when the water vapor from an airplane’s exhaust mixes with the cold air at high altitudes. The interaction between the hot exhaust gases and the cold air causes... Read More