Three major low-cost airlines – EasyJet, Ryanair, and Wizz Air – have teamed up to criticise the airline industry’s main lobby group, the International Air Transport Association (IATA), over its attempt to shield long-haul flights from an EU plan to monitor aircraft vapour trails, also known as contrails.

These airlines accuse IATA of undermining the European Union‘s efforts to study the impact of non-carbon emissions on climate change.

The dispute began when IATA, which represents large airlines like British Airways, Air France, and Lufthansa, wrote a letter to the European Commission urging it to focus its contrail investigation only on flights within Europe. This would exclude long-haul flights, reducing the scope of the EU’s environmental study.

In response, easyJet, Ryanair, and Wizz Air sent a joint letter to the European Commission, arguing that such a narrow focus would “make a mockery” of the EU’s attempt to understand how contrails and other non-CO2 emissions affect global warming.

“Research on non-CO2 suggests that flights outside the EU create significant contrails and that these could have an important warming effect,” the letter reads. “There is no technical reason why extra-EU flights should be exempted from reporting their non-CO2 emissions.”

Long-haul flights account for 52 percent of the airline industry’s carbon emissions, according to the low-cost carriers. If these flights are excluded from the EU’s study, the airlines argue, it would significantly weaken the EU’s climate goals and provide cover for larger airlines like British Airways.

The new EU rules, set to begin in January, require airlines to report non-carbon emissions, including contrails, nitrogen oxides, and sulphur, for all flights departing from the EU.

IATA’s director-general, Willie Walsh, said that monitoring flights in and out of Europe would create a “huge burden” on airlines and suggested the EU should limit its focus to flights within the continent.

However, easyJet, Ryanair, and Wizz Air believe the burden should be shared among all airlines, regardless of whether they operate short-haul or long-haul flights. They find IATA’s attempt to narrow the study’s scope “surprising,” given that some scientists believe contrails could contribute significantly to global warming by forming high-altitude clouds that trap heat.

At the same time, other studies suggest that contrails might also reflect sunlight back into space, which could have a cooling effect.