The company has now taken a significant step toward achieving this goal, completing a flight of a full-scale prototype of its Lilium Jet for the very first time.

Germany-based Lilium sprung out of a business incubator at the European Space Agency (ESA) with the aim of developing a clean and quiet answer to the prickly problem of urban congestion. While there is obviously no one single solution to this, Lilium's approach was to chip away at the problem with an all-electric flying taxi that can be hailed through a smartphone app.

The aircraft would come down and land on pads stationed around cities and regions, and whisk passengers away to their destination, or close to it, without adding to a city's pollution, noise and traffic on the ground.