Contrails

The Federal Aviation Administration (FAA) has established this webpage to provide information to the public on aviation condensation trails (or “contrails” for short). 

  • How contrails form,
  • Research to address persistent contrails, 
  • Public interest in contrails, and
  • Additional resources.

Contrails are created when airplanes fly in cold and humid atmospheric conditions and ice crystals form around the particles emitted from the engine. They predominantly appear as white lines against the blue sky. Contrails tend to be most common and persistent in the sky  when there is excess moisture in the atmosphere.  Natural daily and seasonal variations of wind and atmospheric pressure cause these humid regions to move in the sky.

Last updated: Thursday, July 10, 2025