Uber has moved a step closer in making its ambitious flying car plans a reality by partnering with space agency NASA to provide the technology to make the cars city-friendly by 2020.

The ride-sharing group said NASA will help it to develop both aerial and unmanned traffic management systems for the taxis, meaning they will be able to fly at low altitudes over urban environments.

Uber is not building the four-person 'vertical take-off and landing' cars itself, but has partnered with manufacturers to develop the cars and said it would integrate them into its user network to allow customers to take flights in and around cities.

The vehicles will be able to travel at up to 200mph and will be entirely electric. Uber said the propulsion system for the craft, to be known as uberAIR, will use multiple, small rotors, which will mean they are quiet.

The group first revealed its plans for the "on demand aviation service" last year, and said they would be trialled in Dallas and Dubai. But on Wednesday Uber announced it would also be running demonstrator flights in Los Angeles in 2020.

It expects to cut down a journey time of one hour and twenty minutes down to less than half an hour including transfers to and from the take-off and landing points.