Above: Boeing’s second ecoDemonstrator Explorer, a 737-10 destined for United Airlines, flies with 100% SAF and conventional jet fuel in separate tanks to test SAF’s impact on contrails. The program conducted the tests in the specific temperature and humidity conditions where contrails were likely to be formed. (Boeing photo)
Contrails are increasingly in the news.
Boeing recently announced an innovative study with NASA, United Airlines and other stakeholders to understand how different types of aviation fuels affect the formation of contrails.
So, what exactly are contrails, and what do we know about their climate impact?
Ice: Contrails are clouds made up of ice particles that form when water in the air condenses on aerosols from an aircraft engine exhaust, as well as from other sources, and freezes when exposed to cold temperatures at high altitudes.
Why it matters: Some contrails dissipate quickly and have a negligible climate impact, but those that persist may contribute to either a warming or cooling climate impact, depending on ambient conditions and the timing of formation.
- Studies have estimated that the warming effect from contrails are greater than the cooling effect. Unlike CO2 that can stay in the atmosphere for centuries, contrails are much shorter lived so their warming impacts occur on much shorter timescales. However, there remains high uncertainty on contrail impacts and more research is needed.
Boeing’s role: Boeing is united with its customers and stakeholders on fully understanding and mitigating any negative impacts of non-CO2 aircraft engine combustion emissions on climate change, including contrails.
Go deeper: Read about Boeing’s approach to understanding contrail impacts in this factsheet.
By Ivan Gale