Vertical lift aircraft have existed for more than a century in the form of helicopters. But the $49 billion industry faces a rapidly emerging threat.

An estimated 200 companies are working to build electric vertical takeoff and landing vehicles (eVTOLs), a new type of small passenger aircraft designed for transportation within congested urban environments.

“Helicopters are very expensive to operate for a number of reasons, but the biggest reason is that they have multiple points of failure, which eVTOL aircraft won’t,” said Michael Leskinen, president of United Airlines Ventures, which has invested in startups in the space called Eve and Archer Aviation. “The electrification makes the aircraft safer. Safer aircraft also becomes less costly to maintain.”