Contrails are line-shaped clouds or “condensation trails” composed of ice particles that are visible behind jet aircraft engines under certain atmospheric conditions and at times can persist. EPA is not aware of any deliberate actions to release chemical or biological agents into the atmosphere. If you have a question, please email us at otaq@epa.gov (or call the contrail information line at 734-214-4432 to hear this message).
- Aircraft Contrails Fact Sheet (PDF) (6 pp, 1.6MB, EPA-430-F-00-005, September 2000, reviewed September 2012)
- Contrail Facts from the U.S. Air Force (PDF)(14 pp, 564 K, July 2014)