Plans to bring low-flying air taxi services to Australian cities by companies such as Uber are credible and could be in place within five years, the Civil Aviation Safety Authority says.

CASA spokesman Peter Gibson said he had seen proposals for low-altitude air taxi services that would fly people between locations such as an airport and the central business district of a large city and believed the companies behind the proposals were serious about them.

"There are companies, and I'm talking about big multinational companies, investing big dollars," Mr Gibson said.

"We are talking about hundreds of millions, if not billions."

Uber Air taxis to launch in US

An artist's impression of an Uber air taxi taking off from a building. ( Supplied: Uber )

The comments follow the announcement this year that Uber was considering including Melbourne or Sydney among the launch cities for its Elevate project.

The project involves an electric aircraft able to take people between specific points within a city.

The service was already slated to fly in Dallas and Los Angeles in the United States and the company is considering nine cities, including Sydney and Melbourne, outside the US to trial the project in.

Mr Gibson said Uber had already approached CASA to discuss regulatory issues around the use of air taxis, and he said there were few barriers to what the company was proposing because the regulatory framework to allow it was already there.

"It's a bit like you can just go and charter a helicopter at Brisbane to go to the Sunshine Coast," he said.

"That's all they're doing, but they're doing it in an electric aircraft controlled by a traffic management system and they're doing it a price point cheaper than you could hire a helicopter."

Self-flying vehicles still a long way off

An artist's impression of an Uber Air taxi approaching a landing pad created to promote the company's planned Dallas service. ( Supplied: Uber )

Mr Gibson said the pitch Uber gave to CASA indicated the service would, initially at least, involve human pilots who were able to monitor the aircraft's progress and step in if something went wrong.

The company had said it would need millions of hours of flying time before they would consider allowing the aircraft to operate with complete autonomy.

But developing a traffic management system that would allow aircraft to fly autonomously would be easier than designing one to allow driverless ground vehicles, because there were fewer hazards for the system to deal with.

Multiple companies exploring options in Australia

Mr Gibson said Uber was not the only company looking to Australia because of its easier regulatory environment.

Google's parent company, Alphabet, was preparing to trial drones that made home deliveries in Canberra ahead of trials in the US, partly because the Australian system was more flexible.

And, like Uber, it was an air traffic management system — in this case being developed by Google — that made the project possible.

Mr Gibson noted there were no guarantees the company would select Sydney or Melbourne as one of its launch cities, but there was no question the company was looking hard at Australia.

"Uber is deadly serious about this," he said.