Business Aviation and the Contrail Conundrum

Some business jet operators flying in Europe may be required to add a new element to their flight planning and reporting documentation: impacts from contrail production.

“Starting Jan. 1, 2025, the European Union’s Monitoring, Reporting and Verification (MRV) requirements, which applies to existing U.S.-based flight departments if they have enough European flight activity to trigger compliance with the EU ETS (Emissions Trading System), will expand beyond CO2 impacts,” said Kennedy Ricci, president of 4AIR. “Their goal is to report ‘non-CO2 aviation effects,’ including your impact from contrail production to their [yearly] emissions report.”

Although the new mandate is limited only to some business aircraft operations, it may be time for operators that fly internationally to consider approaches to mitigating contrails.

What’s Wrong With Contrails?

As a quick refresher, condensation trails – more commonly known as contrails – are formed when water vapors and engine exhaust emissions (soot and nitrogen oxide) combine in what are called “ice supersaturation regions.” These regions most commonly occur between altitudes of 35,000 and 41,000 feet, where vapors and emissions rapidly freeze and become artificial cirrus clouds.

According to experts, all high-altitude, cold, cirrus clouds are just thick enough to allow visible sunlight to pass through while, at the same time, trapping infrared radiation (heat) in the lower levels of the atmosphere. Because it’s possible to mitigate production of artificially produced cirrus contrails, climate researchers have singled them out as “a major contributor to the growing greenhouse effect.”

“While some ‘contrail cirrus’ clouds dissipate quickly and have no climate impact, we are interested in the long-duration varieties,” said Matteo Mirolo, head of policy and strategy, contrails for Breakthrough Energy, noting that some scientists say contrails from all aviation segments account for around 1-2% of today’s global warming impacts.

Business aircraft operators are generally quite aware of the issues with contrails and many say they want to do their part to prevent them, but significant hurdles remain. One challenge is predicting the location of areas where contrails will form.

In fact, when jets fly through suspected contrail regions, contrails are not always produced. 4AIR analyzed around 17,000 flights that passed through suspected contrail regions, and only 50 were responsible for half of the entire sample’s contrail footprint, according to Ricci.

“We have two points to consider: First, 2-3% of the flights create 80% of the warming contrails – we’re talking about a small proportion of aircraft,” Mirolo said. “The second point is that most of these warming contrails occur over North America, the North Atlantic and Europe.

“We have a contrails map [at map.contrails.org] that shows you in almost real-time an estimate of where the global aircraft fleet is forming persistent contrails,” said Mirolo. “We can use that information to help pilots and flight planners design courses and trajectories to avoid these areas where the warming contrails are likely to form.

“It’s all a work in progress right now. We need to develop the ability to give a particular direction to each flight to avoid the creation of these warming contrails,” Mirolo said. “We are a non-profit initiative, and we’re working to turn all this research into positive climate action.”

More Contrail Data Needed

Technology is being leveraged in hopes of finding solutions. “Where we really need help right now is getting more data around long-duration contrails and their production,” said Ricci. “In that regard, we’ve created an integration program with ForeFlight where we can actually generate a pre-flight footprint that looks basically like what we already use for icing or turbulence forecasts where you see a vertical extent of the predicted contrail region.

“We’re using it to collect better data on how often we fly into these suspected regions and what our mitigation options may actually be,” he added. “Based on some of the research, we’re seeing that we can fly above these regions on longer trips. We just need to accurately know where they are.”

Contrail Zone Avoidance

You may think that once you know where one of these possible contrail zones is, avoidance is easy. But flight planning as a mitigation tool comes with its own set of challenges. Yes, on long flights, most business jets can efficiently operate above 41,000 feet, but that’s often impractical on shorter trips.

Flying under or around these areas – which often cover hundreds of square miles – isn’t practical because it often requires burning more fuel, which in and of itself increases inflight emissions.

Coordinating Contrail Mitigation With ATC

Another challenge is that flight planning technology and the airspace system aren’t quite in sync yet regarding responsive contrail-mitigation routing.

“I’ve demoed tools from various flight planning companies, and while they have features that may allow you to ‘visualize’ areas of possible contrail development, they’re only part of creating an effective avoidance plan,” said Mike Whannell, CAM, chief pilot at Jack Henry. “Whether or not I understand that a contrail may form at certain altitudes, I may not be able to avoid flying through that area because of ATC restrictions in the area.

“Talking to other operators, if we’re really going to move the needle regarding contrail mitigation, that’s a big discussion we need to have with those who control the NAS (national airspace system) and ATC,” said Whannell, who also serves on NBAA’s Environmental Sustainability Subcommittee. “We need the right people to prioritize this so we can work together to adjust routes and altitudes for all the aircraft flying in a sector, like ATC currently does with supercell avoidance.”

Can SAF Help Mitigate Contrails?

According to experts, when it comes to contrail mitigation, burning sustainable aviation fuel (SAF) is not a silver bullet solution to the problem – at least not yet.

“The industry is doing some research on the impacts of SAF, and we see some potential benefits regarding contrail reductions simply because there are fewer soot particles in the air,” said Ricci. “Research shows that we only see measurable benefits in blends of near 100% SAF. But, right now, the highest percentage blends of SAFs and jet fuel are 50/50 – and typically, it’s 30% SAF and 70% Jet A. They’re doing more studies, but using SAF doesn’t get us all the way to where we need to be.”

“Since contrails are produced by the interaction of soot and water vapor, scientific research shows that reducing soot emissions might reduce the duration and, therefore, the climate impact of these contrails,” Mirolo said. “New engine technologies and fuels could significantly reduce soot emissions, but there are a lot of variables, not the least of which are that these take time to scale up.

“Cleaner burning fuels still may not eliminate contrails as there are still particles emitted that they can form on,” said Mirolo. “So, the best step toward mitigation remains contrail avoidance.”

Review NBAA resources on environmental sustainability at nbaa.org/sustainability.