In 2019, passenger airlines emitted a record 915 million tons of CO² into the atmosphere. But bluer skies may be ahead. Case in point: ZeroAvia’s zero-emission hydrogen-electric power train, which substitutes hydrogen fuel cells and electric motors for conventional fossil-fuel-powered engines. The tech was recently tested on a flight north of London, in which a small Piper M-Class six-seater took to the air. Founder and CEO Val Miftakhov, a pilot and a veteran in the sustainable-transportation industry, predicts that the tech will be able to power a 20-seat aircraft with a range of 500 miles within three years and a 100-passenger jet within 10. —Jesse Will