There is a quiet confidence about the cofounders of VoltAero. A pioneering green aircraft start-up, it has developed a unique parallel electric-hybrid propulsion system that is working. At least 60 companies are now researching and developing fixed-wing electric aircraft, according to Bloomberg research, so it is a crowded market. But there are very few operators as experienced as the founders of VoltAero. Meeting two of its trio of founders in Dublin on Monday, chief executive Jean Botti and director general Marina Evans (the third founder technical director Didier Esteyne is in France), it is hard not to be impressed by…