We still haven't seen the Cassio's final form break out of renders and into real life as yet – we won't even see a scale model until mid-June at the France Air Expo – but VoltAero has been undertaking plenty of test flights to validate its multi-mode hybrid-electric propulsion system, retrofitted into a different airplane called the Cassio-1, since last October. The Cassio-1's cockpit also had to be gutted and rebuilt as well; there are no existing planes designed for hybrid operations.