The race to bring so-called "flying taxis" to market is progressing toward a finish, and Joby Aviation (JOBY 4.90%) appears to be among the companies out in front.

That, and a general shift in market sentiment toward more speculative stocks, helped Joby shares to take flight in December, gaining 11.6% for the month, according to data provided by S&P Global Market Intelligence.

The future is now

It isn't quite what The Jetsons promised us, but in the coming years, it appears a version of flying cars could be coming our way. Joby is one of several aerospace companies racing to develop small electric aircraft capable of vertical takeoffs and landings, or eVTOLs. These vehicles might someday be used as a way to fly over city traffic jams and connect major airports to outer suburbs.

New aircraft types require significant testing and approvals, but Joby, along with fellow start-up Archer Aviation, appear to be leading the way working with the Federal Aviation Administration (FAA) to win approval. Joby also recently became the first electric air taxi to be delivered to the U.S. Air Force, which plans to experiment with the planes and test their usefulness to the service.

December was mostly business as usual for Joby, but the company did announce a few things that would indicate they are still working toward their expected 2025 launch of commercial service. Joby announced a partnership in Japan to develop take-off and landing infrastructure known as vertiports in the country.

The company also completed a series of air-traffic simulations with the National Aeronautics and Space Administration (NASA) designed to show how air taxis can safely be integrated into existing airspace.

In a month when investors were favoring more speculative stocks as hope built that the Federal Reserve's rate-hike campaign was over, investors saw reason to bid up Joby shares.

Is Joby a buy heading into 2024?

As recently as a few years ago, the excitement surrounding these eVOTL companies was overdone. But Joby today trades at a 60% discount to where the stock was in early 2021, and the company's vision for the future is closer to reality than it ever has been. Airlines have bought in as partners, and governments around the world are planning for the eventual arrival of the small planes.

There is still a lot that could go wrong. Regulatory approval is never a given and could take longer than the industry expects. There are at least a half-dozen companies chasing this opportunity, meaning that even if eVOTLs develop as hoped, there will still likely be losers among the manufacturers.

Given the fact that Joby is valued by the market at more than $4 billion despite having little revenue for now, much of that future progress is arguably already priced in.

For those willing to take on a little risk and who are excited about the potential for eVOTLs to transform transportation systems, Joby appears to be the best stock to buy. As a small part of a well-diversified portfolio, Joby stock could end up having the right stuff.