Airlines are finally admitting that contrails are a growing threat to the environment, and they are finally beginning to take action to limit their creation. But what are contrails and what danger do they present? Let’s dive in.

Contrails, a portmanteau of condensation trails, are thin, wispy clouds created when an airplane flies through a cold, humid area in the air. 

The exhaust created by jet engines contains various greenhouse gases like nitrogen oxides, carbon dioxide, carbon monoxide, and water vapor. When the hot, humid exhaust mixes with the cold, dry atmosphere, the water vapor freezes, condensing around the soot from the engine and forming small ice clouds high up in the air. 

These cirrus clouds form an expansive white line that follows the path of the plane for minutes, hours, or even days. Contrails tend to disappear quickly in dry conditions, humidity increases their chances of lasting longer. Specific high-humidity areas known as Ice Super Saturated Regions (ISSRs) can allow contrails to spread and merge with other cirrus clouds, creating massive blanket clouds that can cover thousands of square miles.

While these contrails can be beautiful to admire, they have a devastating impact on the environment, particularly at night. Like any other cloud, contrails trap heat inside Earth’s atmosphere. On the other hand, due to the white color of the clouds, contrails also reflect sunlight back towards space, meaning that they actually have a net cooling effect during the day. 

At night, however, there is no sunlight hitting the Earth at that point. This completely removes the reflecting properties – without sunlight, the contrails do nothing but trap heat in Earth's atmosphere.

Over the past few years, environmentalists and scientists have raised concerns over contrails and the dangers they pose to the global climate. Researchers are just beginning to understand these impacts, but they have already emerged as a silent but deadly environmental killer. 

According to recent studies, the aviation industry accounts for around 2.5% of global carbon dioxide emissions, but around 4% of global warming can be attributed to the sector. Of this 4% share, two-thirds of it comes from non-CO₂ sources, with contrails as the largest contributor. Other studies have confirmed that the environmental impact of contrails is around two to three times as much as that of carbon dioxide, making it a major threat.

Furthermore, studies on aviation’s share of global warming have not taken non-CO₂ sources like contrails into account, suggesting that the industry’s net impact on the environment could be much larger than previously thought.

Despite these concerns, airlines have failed to acknowledge the dangƒers of contrails until now, and almost no action has been taken to stop them. However, there is a simple and easy solution, and airlines are already taking steps towards eliminating long-lasting contrails completely. 

Further research has proven that around 80% of all contrails can be traced back to between 2 and 10% of all flights, suggesting that the problem’s cause is smaller than expected. Experts have confirmed that redirecting those 10% of flights to change their altitude slightly or adjust their flight path can eliminate a large portion of the contrails produced during that time – avoiding ISSRs is key to the process.

Airlines have already begun this process, analyzing planes that are already in the air and locating exactly which areas are most prone to contrail formation. While small changes in flight paths can cause small increases in CO₂ emissions, the contrail-induced warming impact that the process avoids is much, much greater. Additionally, flights that create contrails in the morning or midday can continue with their regular flight paths, as these contrails can actually reflect sunlight back into space and reduce their overall warming effect. 

The Rocky Mountain Institute, a non-profit think tank dedicated to ensuring a smooth transition to clean energy, has already begun a massive project attempting to tackle contrails, involving various major players. They have brought together a cross-sector task force involving Breakthrough Energy, a climate-focused venture capital fund backed by billionaires like Bill Gates, Jeff Bezos, and Michael Bloomberg; Alaska Airlines, American Airlines, Southwest Airlines, United Airlines, and Virgin Atlantic from the airline industry; Airbus and Boeing from the airplane manufacturing industry; Flightkeys, an Austria-based flight planning software company; Google Research, which will help with analytics; and Imperial College London, who have already done several studies on the global impacts of contrails. 

In particular, Google Research has brought artificial intelligence (AI) into the picture, assisting in the analytics portion of the project. Google’s researchers have already begun amassing weather data, satellite data, and flight data to locate ISSRs and detect contrails, with the rest of the team working to feed the data into an AI. The system then processes the information and advises pilots in real time, based off of their likelihood of creating a contrail. The pilots can then adjust altitude or flight path accordingly, minimizing contrail formation. 

An initial round of the project was completed in collaboration with Breakthrough Energy and American Airlines in 2023, involving 70 test flights over six months – they saw a staggering contrail reduction of 54%. 

Nevertheless, airlines are still a long way from implementing this on a more widespread scale, and regulations still need to be adjusted to account for the change in air traffic. In addition, while it is one of the fastest, most efficient ways to reduce the aviation industry’s climate impact, the plan will still require effort and cooperation from various major players.

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