This is what they say: > The Lilium Jet engine has been fully developed in our in-house sound lab where we have used proprietary acoustic modelling software, s

This is what they say: > The Lilium Jet engine has been fully developed in our in-house sound lab where we have used proprietary acoustic modelling software, simulated on high-performance computing clusters, to optimize its design. As well as a customized electric motor, it contains innovative liner technology which means the aircraft will be inaudible from the ground when flying above 400m and will only be as loud as a passing truck while taking off. On the ground, the aircraft will move to and from parking bays using separate electric motors, allowing it to be as quiet as a typical electric car. The usage of future tense (will be) makes me somewhat skeptical