I have 50 years of experience in the aviation industry in both the maintenance and operation of jet aircraft and feel the need to respond to the letter from Alvin Collom regarding aircraft ”contrails” (Journal, Jan. 3).
The temperature where these aircraft operate is normally between minus-50 and minus-70 degrees Fahrenheit. If you look at automobile exhaust in frigid weather, you will observe the same phenomenon that creates “contrails” from aircraft at high altitudes. These visible trails are made up of water vapor, which is a byproduct of the combustion of fossil fuel and varies in opacity in direct proportion to the amount of water vapor in the atmosphere at the altitude the aircraft is flying. At times you will notice these trails stop and start as the aircraft goes in and out of water-vapor plumes in the atmosphere. In minimal moisture, “contrails” are virtually invisible.
This phenomenon was a huge problem for the bomber streams engaged in the daylight bombing of Germany during World War II, and if they could have eliminated it, they most certainly would have.
I have been asked about this many times during my career, and the answer is always the same. It is a natural phenomenon.