Across Europe, flying has become the activity that the environmentally minded love to shun.

Fueled by activists in Sweden and the term “flygskam,” which loosely translates to “flight shame,” the movement has captured the attention of airlines, travel agencies, tour operators and even politicians. The groundswell provoked a defense of air travel from an airline industry trade group official.

“Flying is freedom,” wrote Alexandre de Juniac, director general and CEO of the global airline trade association IATA, in a blog post. “Confining people’s horizons to train distances or boat speeds back-steps on a century of worldwide progress. Relying on virtual meetings to make global connections ignores the feelings and sensations that make us human.”

But the concerns have also prompted action.

On Tuesday, France’s transport minister announced an “eco-tax” on all flights that take off from the country, ranging from 1.5 euros ($1.68) to 18 euros ($20.17). Funds will be used to finance other forms of transportation, including train travel, Reuters reported.

To mark its 100th anniversary, KLM Royal Dutch Airlines recently launched a sustainability campaign that urges travelers to consider flying less, among other actions, especially over short distances when a train would suffice. The carrier says the aviation industry is responsible for 2 to 3% of man-made carbon dioxide emissions globally; IATA puts that number at 2%.

Experts say the trend is well and good in Europe, where rail is widespread and countries are close together. But in the United States, climate-conscious travelers have far fewer options to reduce their carbon footprints.

“One thing that’s different in Europe is that rail is a viable alternative today; for a lot of people, that’s not the case in the U.S.,” says airline expert Seth Kaplan. “A reason why you’re unlikely to see U.S. airlines doing this in any kind of big way is that in the U.S., what’s the alternative?”

Driving is an option, but not always a great alternative for the environment. Speedy train travel across the United States is a dream that may never come true, though the proposed Green New Deal calls for investment in high-speed rail. As it stands, experts say the rail system in the United States takes too long to connect far-flung parts of the country to make it a viable substitute for air travel outside of regions such as the Northeast.

“In most parts of the world, the only way to have less of an environmental impact than flying is not to travel,” Kaplan says.

But, he said, the general feeling is still that traveling is a social good that brings people closer together.

“I think that’s something that people want to feel — that when they travel, they’re mostly doing a good thing,” he says. “And sure, socially conscious people are thinking, ‘Could I do it in some better way?’ ”

One option is to choose carriers such as Spirit, which packs more passengers onto a plane than the roomier, more comfortable competitors. Travelers can also avoid business class or first class, because those seats take up more room on a plane.

“If they were all flying in a dense, economy configuration, the environmental impact would be considerably less because you’d be able to fit all of those seats onto considerably fewer airplanes,” Kaplan says.

In its “Fly Responsibly” campaign, KLM also suggests that passengers pack lighter to reduce weight on a plane so it burns less fuel. The airline offers travelers an easy way to buy offsets for the amount of carbon dioxide emissions generated by their trip and allows other carriers to use its offset program.

“We don’t like to shame,” says Boet Kreiken, KLM’s executive vice president for customer experience. “We frame it as responsible behavior from the airlines, the customers and the industry. That’s a better step than only shaming; that doesn’t solve any issue.”