Send us a textIt’s 20 years since Concorde made its final commercial flight, ending the first era of supersonic travel. A Swiss start-up is part of a new generation of aviation pioneers trying to re-introduce high-speed travel using clean hydrogen. But the road ahead is long and expensive.The article related to this episode and the video interview is available on swissinfo.ch. For other science stories from Switzerland please go to www.swissinfo.ch/science.Video journalist: Julie HuntAudio editor: Michele AndinaDistribution and Marketing: Xin ZhangSWI swissinfo.ch is a public service media company based in Bern, Switzerland.