Europe’s air-safety regulator plans to grade aircraft according to carbon emissions and pollution as passengers demand more information on the environmental impact of flights.

Work has begun on a labeling system similar to that used to rate the efficiency of household appliances such as refrigerators, Patrick Ky, executive director of the European Aviation Safety Agency, said in a briefing on Wednesday.

“Passengers told us they would like to know the environmental performance of the aircraft they are taking,” Ky said in Cologne, Germany. “Customers get smarter and smarter and make more informed decisions about which airlines and airports they use.”

Environmental concerns are becoming a priority for the European Parliament as so-called Green parties win more representation, Ky said. There’s also evidence that passengers in some countries are beginning to make decisions based on emissions, with a slump in Swedish airline bookings and a jump in train travel attributed to the phenomenon of “flygskam” or “flying shame.”

Ky said the eco-labeling could be extended to airlines, airports and possibly maintenance providers. That could be bad news for carriers with older fleets or large numbers of thirsty four-engine jets.

“This is going to be one of the major themes for us for the future,” Ky said. “It is extremely political so we need to be very careful. We want to use indisputable data.”