Cab aggregator Uber on Wednesday said it had teamed up with the United States’ National Aeronautical and Space Administration to build a software to make flying taxis possible. The company, which has already announced plans of flying cars for Dallas and Dubai, said it will begin testing such services in Los Angeles as well by 2020.

The proposed taxis can accommodate four passengers each and fly at a speed of 200 miles an hour, Chief Product Officer Jeff Holden said at an event in Lisbon. He said Uber would seek approvals from aviation regulators before launching these services.

Uber plans to launch paid, intra-city flying taxi services from 2023 in the United States and Europe, Holden told Reuters.

Uber also released a video advertisement for how “UberAir” might look like. It shows a woman booking a flying taxi, going up a nearby rooftop where such cars take off, and entering the “aircraft” to meet Uber staff and co-passengers.

Uber said its deal with Nasa was the first formal services contract by the space agency that covered low-altitude airspace rather than outer space.

Nasa said it had signed a generic agreement in January with Uber, enabling the company to join other industry partners working with the agency to develop driverless air traffic management systems.