A study released last month from the International Council for Clean Transportation shows flying doesn’t contribute too much to the average American’s carbon footprint. In fact, more than half of Americans do not usually fly.

But the United States came in first place for the highest total carbon emissions through commercial aviation activities.

Last year, flights departing from U.S. airports generated nearly one quarter (24 percent) of all carbon dioxide emissions produced by airline operations worldwide. Of that, two-thirds were from domestic flights.

The second-biggest footprint came from China, Hong Kong and Macau, responsible for 13 percent of global emissions. The United Kingdom came in third, with 4 percent, followed by Japan and Germany.

In the United States, the footprint is made bigger by frequent flyers who treat air travel as a luxury rather than a necessity. Just 12 percent of Americans who take more than six round-trip flights a year are making up two-thirds of all U.S. carbon dioxide emissions produced by commercial aviation.

Per traveler, that comes down to three tons of CO2 a year. If this were the norm, global oil consumption would jump 150 percent, and CO2 emissions from fossil fuel use would increase by 60 percent.

Each of those travelers accounts for three tons of CO2 emissions annually. If we all flew like these people, global oil consumption would increase by 150 percent and CO2 emissions from fossil fuel use would rise by 60 percent, said the new report.