Chief technology officers from seven of the world’s major aviation manufacturers issued a joint statement about the future of sustainable aviation on Tuesday at the Paris Air Show. They include Grazia Vittadini of Airbus; Greg Hyslop, Boeing; Bruno Stoufflet, Dassault Aviation; Eric Ducharme, GE Aviation; Paul Stein, Rolls-Royce; Stéphane Cueille, Safran; and Paul Eremenko, United Technologies Corp.

"Aviation connects our world by efficiently and rapidly moving people, opening new economic opportunities, and transporting food and goods all over our planet," the companies said. "At the same time, climate change has become a clear concern for our society. Humanity’s impact on the climate requires action on many fronts. The aviation industry is already taking significant action to protect the planet and will continue to do so."

According to the companies, aviation contributes 2 percent of human-made carbon dioxide emissions, but is growing fast. Thus, the industry is banding together to reduce net CO₂ emissions despite that growth. Through the Air Transport Action Group (ATAG), the aviation industry became the world’s first industrial sector to commit to reducing CO₂ emissions to half of 2005 levels by 2050 and to limit growth of net CO₂ emissions by 2020.

"We are on track to meet those near-term commitments, including the 2019 implementation of the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) program as agreed upon by the nations of the International Civil Aviation Organization (ICAO)," the seven companies noted.

But they're not resting on their laurels. Rolls-Royce's Stein laid out plans to further reduce engine noise, lower emissions by 10 percent, and electrify aviation—though hybrids will likely come first, he said. Ducharme of GE Aviation added that goals to lighten the weight of engines by using lighter materials, as well as to improve aerodynamics, will also help on the propulsion side.

Boeing's Hyslop explained the urgent need for alternative fuels. Current airplanes are ready for—and can handle—these new sources of energy, but the problem lies in obtaining them, he noted. Presently, retrieving alternative fuels is not economically viable, and both infrastructure and incentives are needed to support their production, said Hyslop.

Liquid hydrogen has also shown benefits of lowering combustion temperatures, being a clean energy source, and requiring few materials to produce, according to Dassault's Stoufflet. Despite this, it has a low density, which means a large amount is required to produce the same amount of energy as gasoline, and it also requires both a mass distribution plan and regulations.

According to UTC's Eremenko, the idea of electric propulsion in aviation isn’t new, "But until recently, we hadn’t achieved the power levels and [energy] density necessary to make this dream into a reality." However, he and Safran's Cueille agreed that energy storage and weight are the biggest problems the industry faces, making hybrids a more realistic next step.

Airbus's Vittadini explained that to make aviation more eco-friendly, multiple technological advances must come. This includes new architecture to reduce drag; improved, lighter-weight materials; and engine thermodynamic development to ensure the possibility of this “third generation” of aviation—one of electricity-powered flight.