Uber faces big challenges to get its flying taxi operation into commercial service by 2023, according to leading aviation journal Aviation Week & Space Technology.

The ride-sharing giant has been in Australia recently looking at Sydney and Melbourne to test its air taxi concept in 2020.

But Aviation Week’s Guy Norris said though Uber’s air taxis would be piloted initially, to ease certification and airspace access, its plans to scale up depended on moving to pilotless aircraft as soon as possible.

And surveys have shown that passengers are not willing to trust pilotless planes.

Aside from that challenge, Uber’s concepts are at the cutting edge of technology.

Uber is looking at a variety of vehicles which will be electric vertical take-off and landing vehicles (eVTOLs), most of which look like scaled-up drones.

One concept comes from Boeing subsidiary Aurora Flight Sciences. Its chief executive John Langford told a recent conference that its research indicated that urban air transport would not make money if vehicles were piloted.

Uber plans to have a demonstrator flying by 2020 and certification by 2023. The company plans to focus on Los Angeles and Dallas for its proof of concept flights. Airspace and regulatory issues have emerged as the tough issues, aside from passengers’ acceptance.

To be economically viable, Uber needs to grow the concept to a big scale as quickly as possible.

According to Aviation Week, “initial commercial operations in Dallas/Fort Worth and Los Angeles are planned to use 50 aircraft making 1000 flights a day between a handful of skyports.

“But Uber is looking to networks with 40 nodes and 1000 aircraft making hundreds of thousands of flights a day.”

That was where the challenges became immense, Norris said.