They could do away with the hassle of airports and traffic jams and the cost of hiring pilots, they could fly automatically.

Battery sizes, air traffic control and other infrastructure issues are among the many potential challenges to commercializing them.

“Many things have to happen,” said Sanjiv Singh, professor at the Robotics Institute at Carnegie Mellon University, who co-founded Near Earth Autonomy, near Pittsburgh, which is also working on an eVTOL aircraft.

“If they cost $10 million, no one is going to buy them. If they fly for 5 minutes, no one is going to buy them. If they fall out of the sky every so often, no one is going to buy them,” Singh said in a telephone interview.

The SkyDrive project began humbly as a volunteer project called Cartivator in 2012, with funding by top Japanese companies including automaker Toyota Motor Corp., electronics company Panasonic Corp. and video-game developer Bandai Namco.

A demonstration flight three years ago went poorly. But it has improved and the project recently received another round of funding, of 3.9 billion yen ($37 million), including from the Development Bank of Japan.

The Japanese government is bullish on “the Jetsons” vision, with a “road map” for business services by 2023, and expanded commercial use by the 2030s, stressing its potential for connecting remote areas and providing lifelines in disasters.