In October 2016, Elon Musk said a Tesla vehicle would be able to drive itself across the country by the end of 2017.

It's now 2019, and a Tesla car has yet to drive itself across the country.

Musk now says he expects Tesla cars will be able to operate without any driver intervention by 2020.

In October 2016, Tesla CEO Elon Musk said on a press call that a Tesla vehicle would be able to drive itself across the country, from Los Angeles to New York City, by the end of 2017.

It seemed like an ambitious goal at the time. And it certainly turned out to be more ambitious than Musk, or Tesla, had expected.

In 2015, Musk said he expected a Tesla to be able to drive itself across the country by 2018. When he modified his statement in October 2016, it seemed like Tesla's autonomous-driving system was ahead of schedule.

Now, almost three years later, Tesla's driverless-car goals still seem far away — but Musk keeps making promises anyway.

Just last month, Musk said he was "certain" that Tesla vehicles would be able to operate without driver intervention by the end of 2019, pending regulatory approval.

"I think we will be feature-complete full self-driving this year, meaning the car will be able to find you in a parking lot, pick you up, take you all the way to your destination without an intervention — this year," Musk said in an interview with ARK Invest. "I would say that I am certain of that. That is not a question mark."

But Musk qualified this statement, too, saying updates to Tesla's driverless systems this year would still require drivers to pay attention to the road while Autopilot is active.

In terms of when consumers can expect Tesla cars to fully drive themselves without any driver intervention, Musk estimated in the interview that could happen by the end of next year. He also said both software updates would depend on regulatory approval.

Of course, building cars — and sophisticated car software that can sense its surroundings and make the right decisions to act accordingly — is an extremely difficult endeavor, one that Tesla and rival car companies are still pioneering. And Tesla has made great strides with its Autopilot system, which debuted in 2014. But given how Musk and Tesla continue pushing the timetable for fully autonomous driving, year after year, we wouldn't be surprised to see further delays to this particular goal.

We reached out to Tesla about its ever-changing timeline for self-driving cars. The company declined to comment.