Inside Lilium, the German company trying to revolutionize air travel

German aerospace company Lilium wants to revolutionize air travel with its electric vertical take-off and landing (eVTOL) jet. 

"Revolutionize means make it absolutely zero emission," Lilium CEO Klaus Roewe told CNBC Tech in an interview. 

"We want to make a regional plane that has a decent transport capacity to have a meaningful effect on CO2 emission reduction." 

Less than a decade after being founded by four university students, the group is now one of Europe's leading eVTOL companies. In 2019, Lilium completed a test flight of its all-electric five-seater aircraft. It is targeting certification by 2026. 

"There was a lot of efficiency gain made by the structure, by the systems, notably by the engines. However, you can see it's now coming to a kind of plateau," Roewe said. 

"Getting another 20%-30% out, in terms of CO2 reduction, is very, very difficult. So, you have to make a leapfrog in terms of technologies." 

Lilium, which is backed by the likes of China's Tencent and Earlybird Venture Capital, has started taking orders from the premium market. One jet will cost about $9 million. 

The company is also developing a six-seater version, which will set a buyer back about $7 million. 

The eVTOL space is fiercely competitive, with more than 400 companies and innovators registering designs on the World eVTOL Aircraft Directory. 

However, Daniel Wiegand, Lilium's chief engineer of innovation and future programs, said the company has an offering that is different from its rivals. 

"Most of our peers are using propellers. These propellers have the advantage that they're a bit simpler to design and they need less power in take-off and landing, but they're less efficient in the cruise flight," Wiegand said. 

"We are focused on regional