Aerospace engineers have spent the better part of a century trying to cut weight from aircraft to save on fuel. Deutsche Lufthansa AG is now going the other way on some jets in order to give first-class customers a good night’s rest.

The German group’s Swiss subsidiary will add a lead weight to the tail of some of its aircraft to smooth out a fore-to-aft imbalance caused by its new first class cabin, according to a statement from the company. Engineers will add the so-called “balancing plate” to compensate for the additional weight generated by a new arrangement that will feature lie-down beds and accommodate a maximum of four passengers per aircraft.

“Swiss has decided to remain true to its promise and its aspiration of being a premium air carrier, by committing to retain its First Class cabin on its long-haul aircraft fleet,” the airline said, explaining the need for the weight. The measure will be introduced on Airbus SE A330-300 jets on flights to the US East Coast, Canada and the Middle East. 

The decision to consciously add weight comes as airlines face scrutiny over the environmental impact of flying. Air travel generates about 2% of global greenhouse gas emissions, according to the International Energy Agency. For Swiss, adding weight will further increase fuel burn and thereby the airline’s per-passenger carbon dioxide emissions. 

A single first-class passenger traveling on a round trip from Zurich to New York generates about 14 tons in carbon dioxide, according to climate offset website MyClimate. That’s about five times more than the emissions created by a traveler in economy class, where seats have become more slender and therefore lighter — contributing to the imbalance on the aircraft.