NASA And Partners Explore SAF’s Contrail-Production Qualities


Not to be confused with fanciful speculation about toxic “chemtrails” (chemical trails), actual condensation trails—better known as contrails—have been legitimately shown to contribute to global warming. This is because, just as with any cloud, lingering contrails can trap heat and keep it from escaping the atmosphere. If the aviation industry can minimize the formation of contrails without significant knock-on effects, it would be another way to move toward achieving carbon neutrality.

NASA, Boeing and several other research partners have launched a contrail research initiative in Washington State to explore how contrails from sustainable aviation fuel (SAF) may differ—for better or worse—compared with contrails from engines burning conventional fuels. Flight testing for the program was performed using Boeing’s ecoDemonstrator aircraft. Also involved in the project are GE Aerospace, the German Aerospace Center DLR, the FAA and United Airlines.

According to existing research on contrails, engine exhaust includes both water vapor and soot particles. When the exhaust hits cold air at high altitude, the vapor condenses, and when it interacts with the soot or other particles found in the ambient air, it forms ice crystals. The resulting contrails can remain intact in the upper atmosphere for hours, resulting in localized temperature changes that can adversely affect the temperature of the atmosphere.

For the research flights, Boeing flew its ecoDemonstrator Explorer, a CFM Leap-1B engine-powered 737-10. Over a series of test flights, researchers switched from fuel tanks carrying 100 percent SAF and other tanks with a low-sulfur variant of conventional jet fuel.

A NASA DC-8, described as “the world’s largest flying science laboratory,” flew chase to the 737 to measure emissions and contrail-related ice formations. It is thought that the properties of SAF could be less prone to generating contrails. Results of the study are expected to be released in about 12 months, according to NASA.

Mark Phelps
Mark Phelps is a senior editor at AVweb. He is an instrument rated private pilot and former owner of a Grumman American AA1B and a V-tail Bonanza.

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  1. Are they testing during the day or at night, or both? Seems like during the day, a white cloud increases the “brightness” of earth and reflects solar energy back up/out into space at least as much as it might ‘trap’ energy below. At night maybe it’s a more pronounced heat-retaining result. Overall, it’s just hard to see how contrails make much difference when compared to regular (and much larger) natural clouds.

  2. I seem to remember reading once that contrails helped reflect incoming light back towards space and so reduce warming.
    Can someone give a definitive answer with references? Thanks

    • That’s probably because it isn’t true. Note that the purveyors of this nonsense didn’t provide any backup data.

  3. This is an article that is completely dismissive of the existence of “chem trails” and at the same time treats “global warming” as a serious threat to humanity.
    It’s a case of one guy’s imaginary demon vs. the other guy’s imaginary demon.
    For those of us who are outsiders from both of these ridiculous theories, this whole thing becomes a good laugh.
    Laugh and the whole world laughs with you; cry and you cry alone.

    • Actually, I was GLAD to see mythical “chem trails” dismissed, as they SHOULD be.

      I was disappointed that the article seemed to affirm the equally ludicrous idea of “global warming”, which has been debunked repeatedly. I expect better from people who should know better.

      The “global warming” cult, spurred on by notorious fear monger AlGore, has been predicting that the world would soon be a crispy critter for decades.

      Both the above are nothing more than products of paranoid people with overactive imaginations.

  4. Cirrus and aircraft contrails have a warming affect on the Earth. High level clouds like these allow visible and ultraviolet light coming from the sun to pass thru to the Earth for the most part, but once it hits the Earth it is reflected as infrared light and that can be absorbed by greenhouse gases. The contrails from jet aircraft exhaust can also promote the development of cirrus clouds under the right conditions increasing this effect.