In July, the Dutch airline KLM launched an advertising campaign asking its customers to fly less—a counterintuitive move for a company that makes its profits on, well, flying people places. In a video for its sustainability campaign, “Fly Responsibly,” the airline urges customers to consider the environmental impact of flying: “You want our children to get to know this beautiful world, too. Right?” The ad goes on to challenge customers to consider other modes of travel: “Do you always have to meet face-to-face? Could you take the train instead?” 

The airline’s campaign is just the latest development in a budding European movement that is urging people to consider the climate change impacts of air travel and telling travelers, loudly, You should feel guilty about the climate cost of flying. In Sweden, a grassroots effort has sought to draw attention to the significant carbon footprint of air travel by popularizing the phrase “flygskam,” or “flight shame.” The hashtag-driven campaign appears to be working; according to The Guardian, the number of people using the country’s rail network is surging.

Policymakers in Europe are taking note—and taking aim at the carbon footprint of the airline industry. In July, France announced a new “eco tax” on departing flights that is scheduled to go into effect next year, joining several other European countries including Britain and Sweden that already tax air travel on environmental grounds. Some French members of parliament have even floated the idea of banning short-haul flights that follow routes where a viable rail alternative exists.

With its new campaign, KLM is playing the long game, positioning itself as a sustainability leader in a dirty industry. “I think this may be them trying to get out in front of things,” says airline expert Seth Kaplan. “This is where the world is going. . . . Do you want to be seen as a leader or reactionary?” 

Airline traffic accounts for a sliver of global greenhouse gas emissions—about 2 percent of annual emissions. But that seemingly low number has an outsized impact, and those emissions are fueled by a relatively small number of people. According to an IPCC report on the aviation sector, burning fuel at high altitudes is worse for climate change than combusting fuel on the ground, partially because airplane contrails contribute to warming by trapping additional heat. And while air travel has become habitual for affluent people in the world’s wealthy countries, only a fraction of humanity is responsible for these emissions; according to one estimate, just 18 percent of people alive today have ever stepped foot on an airplane. 

In the past several decades, engineers have succeeded in creating more-fuel-efficient airplanes, but perversely, the carbon footprint of the airline industry today is significantly higher than it was 20 years ago, because efficiency makes flying cheaper, increasing the incentives to fly. “When you are burning less jet fuel, the cost of flying goes down,” Kaplan explains. “That stimulates more people to travel.” 

As the price of air travel falls, more people are buying more flights—and industry projections suggest that aviation emissions will keep increasing. By 2020, aviation emissions are projected to be 70 percent higher than in 2005. By 2050, the global warming effect of air travel and associated contrails could triple, according to one recent study. 

While citizens and policymakers in Europe are debating, often angrily, about the carbon cost of air travel (see, for example, Extinction Rebellion’s attempts to shut down London’s Heathrow airport), flight guilt has yet to take off in the United States. While some influential climate action advocates have sought to draw attention to the issue—like Grist columnist and meteorologist Eric Holthaus, who has pledged to stop flying—it’s fair to say that the subject doesn’t have much traction here.

The relative silence on the issue in the United States is, in part, a result of a lack of easy alternatives to cheap jet travel. “In Europe, a larger percent of the population has greener alternatives,” Kaplan explained. “You can tell people, ‘Just don’t travel,’ but that’s not too appealing. The message that is more appealing is to be able to tell people, ‘Travel, but just do it this other way.’ And in Europe, you can do that in a lot of markets.” 

The network of rail lines crisscrossing the European continent provides a viable alternative to flights for many intra-continental travelers. In the United States, no comparable network of rail lines exists outside of the Northeast. Without an appealing alternative to flights, many US travelers turn a blind eye to the climate change impacts of air travel.

The willful blindness is frustrating because, on an individual level, flying is among our most emissions-intense activities. One round-trip flight from San Francisco to New York, for example, has the same warming impact as over a quarter of the annual carbon dioxide emissions from the average American car. Research indicates that avoiding air travel is one of the single-most significant decisions an individual can make to reduce their carbon footprint—after choosing not to have children and living car-free. According to one estimate, forgoing air travel has a greater climate change benefit than a plant-based diet. Flying is, without question, an environmental sin.

"Sin" is a big word, of course, and it’s important to acknowledge that shame and guilt can be debilitating emotions that may only contribute to the sense of climate despair that already grips too many people. At the same time, guilt and shame can also be productive emotions that can motivate people to change their behaviors for the best. 

The hard truth is that US travelers can’t keep ignoring the climate impacts of flying. Somehow, we must begin to see air travel as a luxury—not the necessity we have come to mistake it for. 

So, what is to be done? One solution is to travel less. If you’re traveling for business, maybe you can take KLM’s suggestion and do a video conference call instead of an in-person meeting. If you’re traveling for pleasure, maybe decide to ditch the weekend getaways in favor of longer (but more infrequent) adventures.

Another solution is to embrace slow travel. We already have a slow food movement that values the local and the artisanal over the global and the industrial. So why not a “slow travel” movement? Instead of hopping on a flight, consider taking the bus or the train to your destination. Yes, it’ll take longer, but there are benefits to winding through the countryside. After all, we miss a lot speeding through the sky. Who knows—by keeping our feet on the earth, we might come to see more of it.