One in five travellers say they'll fly less for the sake of the planet, according to a survey of 6000 travellers as 'flight-shaming' takes off.
The survey predicted environmental concerns would keep denting air traffic, as activists such as Swedish teenager Greta Thunberg lead the way and turn people off planes.
Emma Kemp, a climate change campaigner, said she skipped flying on her last holidays to Italy and Croatia and opted to get around by bus, train and ferry instead.
"I felt I was really travelling," she told Reuters.
"And I felt at peace with myself, having done something for the planet."
If these trends continue, the expected growth in passenger numbers could be halved, Swiss bank UBS said in a report published this week.
The survey took place throughout July and August and showed, on average, one in five travelers in the United States, France, Britain and Germany had cut air travel by at least one flight in the past year because of climate concerns.
Commercial flying accounts for about 2 percent of global carbon emissions and about 12 percent of transport emissions, according to the Air Transport Action Group, an aviation industry group.
The survey also found that the percentage of people thinking of reducing their flying for the same reason had climbed to 27 percent, up from 20 percent in a previous survey during May, 2019.
Any cut in air travel will hit air manufacturers hard, with new plane orders at risk if travellers increasingly turn to trains and boats to travel with a cleaner conscience.
However, the survey doesn't include data from outside of Europe and the United States, where the majority of air travel growth is taking place.
Figures from the International Air Transport Association (IATA) forecast air travel in parts of Asia and Africa to increase by up to 50 percent, and in some places, to double by 2036.
China is forecast to see an increase of over 900 million passengers by 2036, taking the number of travellers within China to 1.5 billion per year.
In Gretta Thunberg's home country of Sweden they've even created a word for the flight shaming phenomenon: 'flygskam.'
The word, its translation as "flight-shaming" in English and the French term "avihonte" are trending on social media.
Germany has announced plans to cut taxes for train journeys and boost levies on flights. And as world leaders met in New York last month, delegates were quick to quiz each other on how they got to New York as 'flight-shame' reached peak attention.
"If there's an elephant in the room... of course it's aviation," Norway's Minister for Climate and Environment Ola Elvestuen told the event.