Qantas Airways Ltd. is the least fuel efficient and burns the most carbon of major airlines that fly across the Pacific Ocean, according to a report by the International Council on Clean Transportation.

Qantas burns an average of one liter of aviation fuel to fly a passenger 22 kilometers, 64 percent more than the 36 kilometers achieved by the region’s two most efficient carriers - Hainan Airlines Holding Co. and All Nippon Airways Co. - according to a study by the researcher that exposed Volkswagen AG’s emissions cheating. The ICCT looked at 20 airlines that operate flights from mainland U.S. to East Asia and Oceania in 2016.

“The reason Qantas ranks low in this study is chiefly because we use larger aircraft, fly very long distances and have premium cabins that naturally have fewer people on board,” Alan Milne, Qantas head of fuel and environment said in an emailed statement.

The report’s authors say the study builds on its earlier work comparing U.S. and European carriers that found airlines with more fuel-efficient aircraft, less premium seating and higher passenger- and freight-load factors operated the most efficient flights. An earlier study found that British Airways Plc was the least fuel efficient carrier to fly the Atlantic in 2014 while Norwegian Air Shuttle ASA was the most efficient.